<PAGE>   1
                                                                   EXHIBIT 10.20

                                    ADDENDUM

        This Addendum is attached to and made a part of that certain Client
Service Agreement (the Agreement) of even date, between Administaff Companies,
Inc. (Administaff), and MHM OF COLORADO, INC. (Client). In the event of a
conflict between this Addendum and the Agreement, this Addendum shall control.


ARTICLE I.   PERSONNEL

        Article I., Personnel, shall be amended to read as follows:

        "Subject to the terms of this Agreement, Administaff agrees to furnish
        Client, and Client agrees to engage form Administaff, employees for the
        job classifications listed, by workers' compensation classification
        codes, in Exhibit A ("Confidential Census"). Client warrants that
        information supplied to Administaff concerning the codes applicable to
        an employee is accurate."


ARTICLE II.  TERM OF AGREEMENT

        Article II, shall be amended to read as follows:

        "This Agreement shall commence on June 30, 1996 and shall remain in
        force and effect until terminated as provided for herein. Either
        Administaff or Client may terminate this Agreement by giving thirty (30)
        days prior written notice."


ARTICLE III. ADMINISTRATION

        Article III, Administration, shall be amended to read as follows:

        "3.1 Administaff and Client recognize that there are a number of federal
        and state statutory, common law and regulatory provisions which define
        the employer-employee relationship. It is the intent of Administaff and
        Client that to the extent permitted by law, "employer" status with
        respect to an employee furnished to Client by Administaff shall be
        determined as set forth in paragraphs 3.2, 3.3, 3.4, and 3.7 and if not
        so determined, shall be based upon the function for which the
        employer-employee relationship is being considered and shall be
        determined in accordance with paragraph 3.6.

        "3.2 Administaff is the employer of those persons furnished to Client
        and is liable as such for the following purposes:


             "a.    compliance with rules and regulations governing the
                    reporting and payment of all federal and state taxes on
                    payroll wages paid under this Agreement including, but

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<PAGE>   2

                    not limited to: (i) federal income tax withholding
                    provisions of the Internal Revenue Code; (ii) state and/or
                    local income tax withholding provisions, if applicable;
                    (iii) Federal Insurance Contributions Act (FICA); (iv)
                    Federal Unemployment Tax Act (FUTA); and (v) applicable
                    state unemployment provisions;

             "b.    except as provided in Paragraph 3.4 g., below, compliance
                    with applicable workers' compensation laws including, but
                    not limited to: (i) procuring workers' compensation
                    insurance; (ii) completing and filing all required reports;
                    and (iii) managing claims;

             "c.    compliance with the Consolidated Omnibus Reconciliation Act
                    (COBRA);

             "d.    compliance with the Immigration Reform and Control Act
                    (IRCA);

             "e.    compliance with the Consumer Credit Protection Act, Title
                    III;

             "f.    procuring and providing employee benefits;


             "g.    monitoring and transmitting to Client changes in
                    governmental regulations relating to policies and practices
                    governing the employer-employee relationship including, but
                    not limited to, issues such as recruiting, interviewing,
                    testing, selecting, orientation of, training, evaluating,
                    replacing, supervision, disciplining and terminating
                    employees.

        "3.3  Client is the employer of those persons furnished by Administaff
        and is liable as such for the following purposes:

             "a.    compliance with Occupational Safety and Health 
                    Administration (OSHA) regulations;

             "b.    compliance with Environmental Protection Agency (EPA)
                    regulations and any state and/or local equivalent;

             "c.    compliance with government contracting provisions including,
                    but not limited to: (i) Executive Order 11246; (ii)
                    Vocational Rehabilitation Act of 1973; (iii) Vietnam Era
                    Veterans' Readjustment Assistance Act of 1974; (iv)
                    Walsh-Healy Public Contracts Act; (v) Davis-Bacon Act; and
                    (vi) Service Contract Act of 1965;

             "d.    compliance with the Fair Labor Standards Act (FLSA);

             "e.    compliance with the Worker Adjustment and Retraining
                    Notification Act (WARN); provided, however, that so long as
                    Client is an employer of less than the

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<PAGE>   3


                    number of employees required to make Client subject to
                    the application of WARN, and if Client would not otherwise
                    be subject to the jurisdiction or application of WARN but
                    for the fact that Administaff is an employer of more than
                    the jurisdictional minimum number of employees required for
                    the compliance with WARN then Administaff shall be
                    responsible for compliance with WARN, in which case Client
                    covenants and agrees that it shall give Administaff no less
                    than ninety (90) days notice of (i) the closing or shut
                    down of an employment site (or one or more facilities or
                    operating units within an employment site) resulting in an
                    employment loss for fifty (50) or more employees during any
                    thirty (30) day period; (ii) the mass layoff of employees
                    which does not result in the closing or shut down of an
                    employment site but which will result in the loss of
                    employment during any thirty (30) day period for 500 or
                    more employees, or for 50 to 499 employees if they make up
                    at least 33% of the work force; or (iii) any combination of
                    the closing of an employment site or mass layoff of
                    employees which would not individually trigger the WARN
                    notice requirement if it occurred within a thirty (30) day
                    time period, but which taken together during any ninety
                    (90) day time period reaches the threshold level of
                    employment loss that would require Administaff to give
                    notice;

             "f.    compliance with any professional licensing requirements;

             "g.    compliance with any fidelity bonding requirements;

             "h.    professional liability, including but not limited to
                    malpractice or errors and omissions coverage and compliance
                    with any regulation mandating such coverage;

             "i.    Section 414(o) of the Internal Revenue Code (avoidance of
                    certain pension and non-pension employee benefit
                    requirements) (except as provided in paragraph 3.4c below);

             "j.    the rendering of professional medical services, including,
                    but not by way of limitation, the services of a psychologist
                    and the diagnosis and treatment of all patients under the
                    Client's care; it being specifically acknowledged and agreed
                    that Administaff's duties, responsibilities and functions
                    hereunder shall be administrative and managerial in nature
                    only, and that notwithstanding any other provision of this
                    Agreement to the contrary, Administaff shall engage in no
                    activity hereunder that would constitute the corporate
                    practice of medicine as defined by applicable laws in any
                    jurisdiction in which the corporate practice of medicine is
                    prohibited. The parties understand and agree that Client has
                    the sole responsibility for the coordination and provision
                    of all medical services and Administaff shall not interfere
                    in any way with the exercise of the professional medical
                    judgment of Client or Client's providers in connection with
                    their practice of medicine. All of Client's policies and


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<PAGE>   4



                    procedures relating to the governance of its physicians or
                    psychologists who will work under the direction of Client or
                    its physicians or psychologists shall be adopted from time
                    to time in the sole discretion of Client, its shareholders
                    and board of directors, as applicable. Such policies may
                    include practice standards, peer review and corrective
                    action, disciplinary matters, on-call schedules, referral
                    physician panel and services, clinical procedures,
                    utilization management and quality management procedures,
                    credentialing, appointment and replacement of Association
                    medical directors, patient care decisions, physician and
                    other licensed health care professional compensation and
                    incentives, physician training, continuing education,
                    development and supervision and shareholder eligibility.
                    Should any function assigned to Administaff hereunder be
                    construed to be within the practice of medicine such that,
                    if performed by Administaff, it would be violative of
                    applicable prohibitions on the corporate practice of
                    medicine, such function thereafter shall be assigned to and
                    become the responsibility of Client and any such prior
                    activities which were undertaken by Administaff shall be
                    considered to have been undertaken by Client.

         "3.4 Administaff and Client will be considered co-employers ("dual or 
         joint employers") of those persons furnished to Client by Administaff 
         for the following purposes:

             "a.    compliance with Title VII of the 1964 Civil Rights Act;

             "b.    compliance with the Age Discrimination in Employment Act
                    (ADEA);

             "c.    compliance with the Employee Retirement Income Security Act
                    (ERISA) (except as provided by paragraph 3.3i above);

             "d.    compliance with the Polygraph Protection Act;

             "e.    compliance with the Federal Drug Free Workplace Act and any
                    state and/or local equivalent;

             "f.    compliance with state employment discrimination laws;

             "g.    employer liability under workers' compensation laws;

             "h.    implementation of policies and practices relating to the
                    employer-employee relationship such as recruiting,
                    interviewing, testing, selecting, orientation of, training,
                    evaluating, replacing, supervision, disciplining and
                    terminating employees; and


                                     Page 4



<PAGE>   5
             "i.    selection of fringe benefits, including, but not limited to,
                    holidays, vacation, sick leave, parental leave, military
                    leave, and leave of absence.

        "3.5 Nothing in paragraphs 3.2, 3.3, 3.4, or 3.7 shall be construed to
        require either Administaff or Client to perform any matter not referred
        to therein; provided that the foregoing shall not affect the obligation
        of Administaff or Client to perform any matter required by law or as
        otherwise specifically provided by this Agreement.

        "3.6 For purposes of this Agreement, determination of employer status 
        for situations not set forth and not contemplated herein shall be made 
        by mutual agreement of Administaff and Client.

        "3.7 Client is the employer of those persons furnished by Administaff
        (i) with respect to the assignment and ownership of all intellectual
        property rights including, but not limited to, inventions, whether
        patentable or not, and patents resulting therefrom, copyrights and trade
        secrets; and (ii) with respect to any confidentiality agreements
        regarding proprietary information and any covenant not to compete.


ARTICLE VI.  SERVICE FEE

        Article VI., Service Fee, Paragraph 6.3 (i) shall be amended to read as
follows:

        "6.3 ADMINISTAFF shall not adjust the fee rate percentage for Client
        more often than once annually during the term of this Agreement except
        for adjustments made necessary by:

             "(i)   statutory and regulatory changes including, but not limited
                    to, adjustments to FICA and federal and/or state 
                    unemployment taxes and workers' compensation; and/or;

             "(ii)  changes in the information supplied on Exhibit A
                    (Confidential Census) initiated by Client to the extent that
                    such change, when applied to the recalculation of the fee
                    rate percentage, causes an increase or decrease of at least
                    one fee rate percentage point."

        Article VI., Paragraph 6.5 shall be amended to read as follows:

        "6.5 Any increases in the fee rate percentages for statutory or
        regulatory changes in employment taxes, insurance costs or job
        functions shall be effective on the date of such statutory or regulatory
        increase or change. Any such increase shall be no greater than the
        amount necessary to cover the cost to Administaff of the increase in
        employment taxes, insurance costs, or costs resulting from the change in
        job functions."


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<PAGE>   6
        Article VI., Paragraph 6.8, shall be amended to read as follows:

        "6.8 The fee provided for by this Agreement shall be due and payable at
        least one (1) working day prior to the date of payroll delivery. So long
        as Client is timely in the reporting of payroll information and payment
        of the fee provided for by this Agreement Administaff shall make payroll
        delivery to the employees furnished to the Client on the regularly
        scheduled payday. In addition Administaff shall provide Client on each
        payday with a report of the accrued leave for each employee furnished to
        Client (including the leave currently accrued by each employee while
        employed by Client prior to the effective date of this Agreement,
        provided that such information is timely and accurately provided to
        Administaff by Client for inclusion on the payday accrued leave
        report)."


ARTICLE VII.   INSURANCE

        "7.1 Administaff shall furnish and keep in full force and effect at all
        times during the term of this Agreement, workers' compensation insurance
        covering all Administaff employees furnished to Client pursuant to the
        terms of this Agreement. Upon written request by Client, Administaff
        shall furnish a certificate of insurance verifying such coverage. Such
        workers' compensation coverage will comply with applicable law."


ARTICLE IX.  DEFAULT

        Article IX., Default, Paragraph 9.3 shall be amended to read as
follows:

        "9.3 In the event that this Agreement is terminated due to a default by
        Client, Client shall pay Administaff a sum equal to the fee rate
        percentage multiplied by the estimated gross payroll for a thirty day
        period as liquidated damages, but such payment does not release Client
        from its obligations under this Agreement, or from liability for future
        breach of such obligations."

        Article IX., Default, shall be amended to add Paragraphs 9.5, 9.6, and
        9.7 as follows: 

        "9.5 Acts of default by Administaff shall include, but are not limited
        to: 

             "a.    failure to pay wages to leased employees;

             "b.    failure to pay payroll taxes to a federal, state, or local
                    governmental body, department or agency when due;

             "c.    failure to pay premiums to an insurance carrier providing
                    coverage to Administaff employees leased to Client;

             "d.    violation by Administaff of any provision of this
                    Agreement."

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<PAGE>   7



        "9.6 Upon an act of default by Administaff, Client shall have the
        option, in its sole and absolute discretion, of terminating this
        Agreement, and in the event Client exercises such option, this Agreement
        shall terminate on the date written notice of same is delivered to
        Administaff."

        "9.7 In the event Client incurs any expenses, fines and/or liabilities
        as a result of an act of default by Administaff as set forth above,
        Administaff shall reimburse Client for all actual expenses, fines and/or
        liabilities, including, but not limited to, reasonable attorneys' fees,
        court costs and any related expenses."


ARTICLE X.   INDEMNITY

        Article X., Indemnity, Paragraph 10.3, shall be amended to read as
follows:

        "10.3 Client and Administaff expressly agree that the indemnification
        provisions of this Agreement shall not be limited to claims, expenses,
        or liabilities for which one of them is solely liable, but shall also
        apply to claims, expenses and liabilities for which Client and
        Administaff are jointly or concurrently liable. In such event, if either
        of them advances funds or makes any other payment in connection with a
        claim, expense or liability which is subject to this Article X in excess
        of its pro rata share, said party shall be indemnified by the other
        party hereto for such excess amounts."


ARTICLE XI.  MISCELLANEOUS

        Article XI., Miscellaneous, Paragraph 11.2, shall be amended to read as
follows:

        "11.2 Client and Administaff warrant and represent to each other that,
        prior to the commencement of this Agreement, no separate agreements or
        arrangements exist between the parties that would obligate Client or
        Administaff except as set forth herein."

        Article XI., Miscellaneous, Paragraph 11.4 shall be amended to read as
follows:

        "11.4 Client agrees to comply, at its sole cost and expense, with any
        applicable specific directives promulgated by: (i) a federal, state, or
        local governmental body, department, or agency, (ii) an insurance
        carrier providing coverage to Administaff and/or its employees affecting
        this Agreement and/or, (iii) Administaff as made necessary by
        circumstances which currently or specifically affect Administaff, Client
        or Administaff's employees except where such compliance is otherwise the
        responsibility of Administaff under the terms of this Agreement."



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<PAGE>   8


        Article XI., Miscellaneous, shall be amended to add Paragraph 11.7 as
        follows:

        "11.7 Administaff hereby warrants that (i) the scope of benefits
        available to eligible employees under the Administaff Benefit Plan (the
        Administaff Plan) on the effective date of this Agreement are
        substantially the same as are stated in the attached pamphlet entitled
        Outline of Benefits attached; (ii) Administaff will give notice of any
        material change in the Administaff Plan to all eligible participants at
        least thirty-five (35) days prior to the effective date of such material
        change; (iii) pre-existing conditions are covered by the Major Medical
        Plan (the Administaff Medical Plan) which is part of the Administaff
        Plan; (iv) amounts paid by a covered employee to defray a covered
        expense under the Client's existing health or medical benefit plan
        (Client's Plan) toward the deductible or co-payment requirements of
        Client's Plan will be credited and apply to the satisfaction of the
        deductible or co-payment requirement of the Administaff Medical Plan
        provided that the amount paid otherwise satisfies the criteria for
        credit or application to the satisfaction of the deductible or
        co-payment requirements of the Administaff Medical Plan and its usual
        proof of payment criteria; and (v) a former employee of Client which is
        covered by COBRA under Client's Plan on the effective date of this
        Agreement will be eligible for COBRA coverage under Administaff's
        Medical Plan provided that Client has fully disclosed the scope and
        extent of such existing COBRA coverage to Administaff prior to the
        execution of this Agreement."


XVI.  ENTIRE AGREEMENT

        Article XVI., Entire Agreement, shall be amended to read as follows:

        "This instrument, including the Exhibits attached hereto, contains the
        entire Agreement of the parties and supersedes all prior and
        contemporaneous agreements or understandings, whether written or oral,
        with respect to the subject matter hereof.  No amendment or modification
        hereto shall be valid unless in writing and signed by both parties
        hereto other than changes to Exhibit A (Confidential Census) from time
        to time as may be necessary in the operation of Client's business and
        the performance of the parties of their respective obligations under
        this Agreement."

        This Addendum is executed and effective of even date with the Client
Service Agreement dated June 30, 1996, between the parties hereto to which it is
attached and incorporated by reference.

ADMINISTAFF COMPANIES, INC.                 MHM OF COLORADO, INC.


By:  /s/ A. STEVE ARIZOF                    By:  /s/ MICHAEL PINKERT
   ----------------------------                ------------------------------
                Vice President                                      President

-------------------------------             ---------------------------------
Name: Typed or Printed                      Name: Typed or Printed


                                     Page 8






<PAGE>   9



        ADMINISTAFF(R)
                            CLIENT SERVICE AGREEMENT

THIS CLIENT SERVICE AGREEMENT ("the Agreement"), is made by and between
Administaff Companies, Inc., ("Administaff"), a Delaware corporation with its
principal place of business at 19001 Crescent Springs Drive, Kingwood, Texas
77339-3802, and MHM of Colorado, Inc ("Client"). 

                                  I. PERSONNEL

Subject to the terms of this Agreement, Administaff agrees to furnish Client,
and Client agrees to engage from Administaff, employees for the job functions
listed in Exhibit A ("Confidential Census").  Client warrants that information
supplied to Administaff concerning the employee functions is accurate.

                              II. TERM OF AGREEMENT

This Agreement shall commence on the date this Agreement is executed and remain
in force and effect for a term of one (1) year ("Initial Term"). Following the
Initial Term, this Agreement shall remain in full force and effect for
successive monthly terms (the "Extended Terms") until either (i) the Agreement
is renewed; or, (ii) the Agreement is terminated. During the Initial Term, and
any Extended Term of this Agreement, either Administaff or Client may terminate
this Agreement by giving thirty (30) days prior written notice.

                              III. ADMINISTRATION

3.1  There are a number of federal and state statutory, common law and
regulatory provisions which define the employer-employee relationship.
"Employer" status is based upon the function for which the employer-employee
relationship is being considered.

3.2  Administaff is the employer of those persons furnished to Client and listed
on Exhibit A and is liable as such for the following purposes:

     a.   compliance with rules and regulations governing the reporting and
          payment of all federal and state taxes on payroll wages paid under
          this Agreement including, but not limited to: (i) federal income tax
          withholding provisions of the Internal Revenue Code; (ii) state and/or
          local income tax withholding provisions, if applicable; (iii) Federal
          Insurance Contributions Act (FICA); (iv) Federal Unemployment Tax Act
          (FUTA); and (v) applicable state unemployment provisions;

     b.   except as provided in Paragraph 3.4g below, compliance with applicable
          workers' compensation laws including, but not limited to: (i)
          procuring workers' compensation insurance; (ii) completing and filing
          all required reports; and (iii) managing claims;

     c.   compliance with the Consolidated Omnibus Reconciliation Act (COBRA);

     d.   compliance with the Immigration Reform and Control Act (IRCA);

     e.   compliance with the Consumer Credit Protection Act, Title III;

     f.   procuring and providing employee benefits;

     g.   monitoring and transmitting to Client changes in governmental
          regulations relating to policies and practices governing the
          employer-employee relationship including, but not limited to, issues
          such as recruiting, interviewing, testing, selecting, orientation of,
          training, evaluating, replacing, supervision, disciplining and
          terminating employees.

3.3  Client is the employer of those persons furnished by Administaff and listed
on Exhibit A and is liable as such for the following purposes:

     a.   compliance with Occupational Safety and Health Administration (OSHA)
          regulations;

     b.   compliance with Environmental Protection Agency (EPA) regulations and
          any state and/or local equivalent;

     c.   compliance with government contracting provisions including, but not
          limited to: (i) Executive Order 11246; (ii) Vocational Rehabilitation
          Act of 1973; (iii) Vietnam Era Veterans' Readjustment Assistance Act 
          of 1974; (iv) Walsh-Healey Public Contracts Act; (v) Davis-Bacon Act'
          and (vi) Service Contract Act of 1965;

     d.   compliance with the Fair Labor Standards Act (FLSA);

     e.   compliance with the Worker Adjustment and Retraining Notification Act
          (WARN);

     f.   compliance with any professional licensing requirements;

     g.   compliance with any fidelity bonding requirements;

                                       1

<PAGE>   10



     h.   professional liability, including but not limited to malpractice or
          errors and omissions coverage and compliance with any regulation
          mandating such coverage;

     i.   Section 414(o) of the Internal Revenue Code (avoidance of certain
          pension and non-pension employee benefits requirements) (except as
          provided in paragraph 3.4c below);

     j.   assignment to, and ownership of all intellectual property rights
          including, but not limited to, inventions, whether patentable or not,
          and patents resulting therefrom, copyrights and trade secrets and all
          confidentiality agreements regarding proprietary information.

3.4  Administaff and Client will be considered co-employers ("dual or joint
employers") of those persons furnished to Client by Administaff and listed on
Exhibit A for the following purposes:

     a.   compliance with Title VII of the 1964 Civil Rights Act;

     b.   compliance with the Age Discrimination in Employment Act (ADEA);

     c.   compliance with the Employee Retirement Income Security Act (ERISA)
          (except as provided by paragraph 3.3i above);

     d.   compliance with the Polygraph Protection Act;

     e.   compliance with the Federal Drug Free Workplace Act and any state
          and/or local equivalent;

     f.   compliance with state employment discrimination laws including, but
          not limited to, Article 5221k, Texas Revised Civil Statues;

     g.   employer liability under workers' compensation laws;

     h.   implementation of policies and practices relating to the
          employer-employee relationship such as recruiting, interviewing,
          testing, selecting, orientation of, training, evaluating, replacing,
          supervision, disciplining and terminating employees; and

     i.   selection of fringe benefits, including, but not limited to, holidays,
          vacation, sick leave, parental leave, military leave, and leave of
          absence.

3.5  Nothing in paragraphs 3.2, 3.3 or 3.4 above shall be construed to require
either Administaff or Client to provide any of the matters referred to therein
except as provided by law or as otherwise specifically provided by this
contract.

3.6  For the purposes of this Agreement, determination of employer status for
situations not set forth and not contemplated herein shall be made by mutual
agreement of Administaff and Client.


                                 IV. SUPERVISION

Administaff shall designate one or more on-site supervisors from among its
employees furnished to Client and listed on Exhibit A. On-site supervisors shall
direct operational and administrative matters relating to services provided by
Administaff's employees and shall carry out Administaff's policies and
procedures formulated in accordance with Paragraph 3.4h above.


                                V. ENROLLMENT FEE

Client agrees to pay Administaff a non-refundable enrollment fee in the sum
specified in Exhibit B (Client Service Application). This enrollment fee is due
and payable at the time that this Agreement is signed by Client.


                                 VI. SERVICE FEE

In exchange for the personnel services provided by Administaff hereunder,
Administaff and Client agree as follows:

6.1  The Administaff fee rate percentage is set forth in Exhibit B (Client
Service Application) and is calculated utilizing the data submitted by Client
in Exhibit A. If such information is inaccurate, Client shall immediately agree
to amend Exhibit A to reflect the current information and shall pay, within     
ten (10) days notice from Administaff of the error, any additional costs
incurred by Administaff as a result of the inaccuracy.

6.2  Each pay period, Client shall pay Administaff its fee comprised of: (i) the
gross payroll of Administaff employees leased to Client during such pay period;
and, (ii) a service fee equal to the fee rate percentage specified in Exhibit B
multiplied by the actual gross payroll of Administaff employees furnished to
Client during such pay period.

6.3  Administaff shall not adjust the fee rate percentage for Client during any
term of this Agreement except for adjustments made necessary by:

                                        2



<PAGE>   11

     (i)  statutory and regulatory changes, including, but not limited to,
          adjustments to FICA, federal and/or state unemployment taxes and
          workers' compensation; and/or

     (ii) changes in the information supplied on Exhibit A (Confidential Census)
          initiated by Client to the extent that such change, when applied to
          the recalculation of the fee rate percentage, causes an increase or
          decrease of at least one fee rate e point. 


6.4  In addition to the foregoing, during any Extended Term Administaff may
adjust the fee rate percentage upon thirty (30) days written notice to Client.

6.5  Any increases in the fee rate percentages for statutory or regulatory
changes in employment taxes, insurance costs or job functions shall be
effective on the date of such statutory or regulatory increase or change.

6.6  Any increase in the fee will be billed with the next effective
payroll and be kept current at all times except for retroactive changes or
statutory and/or regulatory changes known at the time the payroll is billed.

6.7  Any change in the fee rate percentage shall be reflected in a revised
Exhibit B which shall then be made a part of this Agreement.

6.8  The fee provided for by this Agreement shall be due and payable at least 
one (1) working day prior to the date of payroll delivery.

6.9  Client shall use a method of payment approved in advance by Administaff.

6.10 Client or on-site supervisor shall report to Administaff all time worked by
all Administaff employees furnished to Client each pay period and shall provide
Administaff with written verification of same.

6.11 Client shall notify Administaff within two (2) working days of any error in
billing.

6.12 Client shall reimburse Administaff for services not contemplated by this
Agreement which may be required by Client.

                                 VII. INSURANCE

7.1  Administaff shall furnish, and keep in full force and effect at all times
during the term of this Agreement, worker's compensation insurance covering all
Administaff employees furnished to Client pursuant to the terms of this
Agreement. Upon written request by Client, Administaff shall furnish a
certificate of insurance verifying such coverage.

7.2  Client shall furnish, and keep in force and effect at all times during the
term of this Agreement, comprehensive general liability insurance including
products/completed operations coverage with minimum limits of $1,000,000 per
occurrence and $2,000,000 aggregate. Client shall cause its insurance carrier to
issue a certificate of insurance to Administaff, Inc. confirming this coverage
and to give not less than thirty (30) days advance notice of cancellation or
material change.

7.3  Client shall furnish, and keep in force and effect at all times during the
term of this Agreement, comprehensive automobile liability insurance covering
all owned, hired and non-owned automobiles with a minimum limit of $1,000,000
per occurrence combined single limit bodily injury and property damage
liability. The policy shall also provide uninsured motorists insurance with a
minimum combined single limit of Sixty Thousand Dollars ($60,000.00). In states
where "no fault" laws apply, Personal Injury Protection (P.I.P.) or equivalent
coverage shall be required to meet the requirements of the state. The client
shall cause its insurance carrier to issue a certificate of insurance to
Administaff, Inc. confirming this coverage and to give not less than thirty (30)
days advance notice of cancellation or material change.

7.4  Client shall deliver copies of all insurance certificates required pursuant
to this Article signed by authorized representatives of the insurance companies
to Administaff within fifteen (15) days of the commencement date of this
Agreement.

                           VIII. EMPLOYMENT AGREEMENT

Each employee furnished by Administaff to Client and listed on Exhibit A shall
be required to execute an Employment Agreement as set forth in Exhibit C
(Employment Agreement Form) before such employee shall commence the term of
assignment with Client.

                                   IX. DEFAULT

9.1  Acts of default by Client shall include, but are not limited to:

     a.   failure of Client to pay a fee when due;

     b.   failure of Client to comply within thirty (30) days of any directive
          of Administaff, when such directive is promulgated or made necessary
          by: (i) a federal, state or local governmental body, department or
          agency; or (ii) an insurance carrier providing coverage to Administaff
          and/or its employees;




                                        3
     

<PAGE>   12

     c.   direct payment of taxable wages by Client to Administaff employees for
          services contemplated by this Agreement;

     d.   commission or omission of any act that usurps any right or obligation
          of Administaff as an employer of the employees covered by this
          Agreement; and/or,

     e.   violation by Client of any provision of this Agreement.

9.2 In the event Administaff incurs any expenses, fines and/or liabilities as a
result of an act of default by Client as set forth above, Client shall
reimburse Administaff for all actual expenses, fines and/or liabilities,
including, but not limited to, reasonable attorneys' fees, court costs and any
related expenses.

9.3 In the event that this Agreement is terminated due to a default by Client,
Client shall pay Administaff a sum equal to the fee rate percentage multiplied
by the estimated gross payroll for the remaining contract period as liquidated
damages, but such payment does not release Client from its obligations under
this Agreement, or from liability for future breach of such obligations.

9.4 Upon an act of default by Client other than under Paragraph 9.lc above,
Administaff shall have the option, in its sole and absolute discretion, of
terminating this Agreement, and in the event Administaff exercises such option,
this Agreement shall terminate on the date written notice of same is delivered
to Client. In the event, however, of an act of default by Client under
Paragraph 9.1c above, Administaff shall have the option in its sole and
absolute discretion of terminating this Agreement effective on the date of such
act.

                                  X. INDEMNITY

10.1 Client thereby agrees to indemnify, defend and hold Administaff harmless
from and against any and all liability, expense (including court costs and
attorneys' fees) and claims for damage of any nature whatsoever, whether known
or unknown and whether direct or indirect, as though expressly set forth and
described herein, which Administaff may incur, suffer, become liable for or
which may be asserted or claimed against Administaff as a result of the acts,
errors or omissions, including negligent acts and statutory violations, of
Client.

10.2 Administaff hereby agrees to indemnify, defend and hold Client harmless
from and against any and all liability, expense (including court costs and
attorneys' fees) and claims for damage of any nature whatsoever, whether known
or unknown and whether direct or indirect, as though expressly set forth and
described herein, which Client may incur, suffer, become liable for or which
may be asserted or claimed against Client as a result of the acts, errors or
omissions, including negligent acts and statutory violations, of Administaff.

10.3 Client and Administaff expressly agree that the indemnification provisions
of this Agreement shall not be limited to claims, expenses, or liabilities for
which one of them is solely liable, but shall also apply to claims, expenses
and liabilities for which client and Administaff are jointly and concurrently
liable. In such event, if either of them advances funds in connection with a
claim, expense or liability which is subject to this Article X in excess of its
pro rata share, said party shall be indemnified by the other party hereto for
such excess amounts.


                               XI. MISCELLANEOUS

11.1 This Agreement may be amended from time to time as agreed by the parties
in writing. Such amendment shall become effective on the date so designated
when signed by both Administaff and Client.

11.2 Client and Administaff warrant and represent to each other that, prior to
the commencement of this Agreement, no separate agreements or arrangements
exist that would obligate Client or Administaff except as set forth herein.

11.3 Client and Administaff agree to immediately report to each other all
accidents and injuries involving Administaff employees as signed to Client.

11.4 Client agrees to comply, at its sole cost and expense, with any applicable
specific directives promulgated by: (i) a federal, state or local governmental
body, department or agency, (ii) an insurance carrier providing coverage to
Administaff and/or its employees affecting this Agreement, and/or (iii)
Administaff as made necessary by circumstances which currently or specifically
affect Administaff, Client or Administaff's employees.

11.5 This Agreement is between Administaff and Client and creates no individual
rights of Administaff employees as against Client.

11.6 Administaff and Administaff's workers' compensation insurance carrier
shall have the right to inspect Client's premises, including any job site to
which Client assigns Administaff's employees. To the extent possible, such
inspection shall be scheduled at a mutually convenient time.


                                XII. ARBITRATION

12.1 Administaff and Client agree and stipulate that all claims, disputes and
other matters in question between Administaff and Client arising out of, or
relating to this Agreement or the breach thereof will be decided by arbitration
in accordance with the Federal Arbitration Act (9 U.S.C. Sections 10 and 11)
and the Commercial Arbitration Rules of the American Arbitration Association
then obtaining subject to the limitations of this Article XII. This agreement
to so arbitrate and any other agreement or consent to arbitrate entered into in
accordance herewith as provided in this Article XII will be specifically
enforceable under the prevailing law of any court having jurisdiction.


                                        4

<PAGE>   13


12.2 Notice of the demand for arbitration will be filed in writing with the
other party to the Agreement and with the American Arbitration Association. The
demand for arbitration shall be made within a reasonable time after the claim,
dispute or other matter in question has arisen, and in no event shall any such
demand be made after the date when institution of legal or equitable proceedings
based on such claim, dispute or other matter in question would be barred by the
applicable statute of limitations.

12.3 No arbitration arising out of, or relating to, this Agreement shall include
by consolidation, joinder or in any other manner any other person or entity who
is not a party to this contract unless:

     a.   the inclusion of such other person or entity is necessary if complete
          relief is to be afforded among those who are already parties to the
          arbitration, and/or such other person or entity is substantially
          involved in a question of law or fact which is common to those who are
          already parties to the arbitration and which will arise in such
          proceedings; and,

     b.   the written consent of the other person or entity sought to be
          included and Administaff and Client has been obtained for such
          inclusion, which consent shall make specific reference to this
          paragraph; but no such consent shall constitute consent to arbitration
          of any dispute not specifically described in such consent or to
          arbitration with any party not specifically identified in such
          consent.

12.4 The award rendered by the arbitrators will be final, judgment may be       
entered upon it in any court having jurisdiction thereof, and will not be
subject to modification or appeal except to the extent permitted by Sections 10
and 11 of the Federal Arbitration Act (9 U.S.C. sections 10 and 11).

                                XIII. ASSIGNMENT

Neither party shall assign this Agreement or its rights and duties hereunder, or
any interest herein, without the prior written consent of the other party. 

                             XIV. ATTORNEYS' FEES

The prevailing party in any enforcement action arising in respect to this 
Agreement shall be entitled to recover from the other party all costs of
such enforcement action including, without limitation, reasonable attorneys'
fees, court costs and related expenses.

                                XV. GOVERNING LAW

EXCEPT FOR ARTICLE XII OF THIS AGREEMENT, WHICH SHALL BE GOVERNED BY THE FEDERAL
ARBITRATION ACT (9 U.S.C. sections 10 AND 11), THIS AGREEMENT SHALL BE
GOVERNED BY THE LAWS OF THE STATE OF TEXAS.

                              XVI. ENTIRE AGREEMENT

This instrument, including the Exhibits attached hereto, contains the entire
Agreement of the parties and supersedes all prior and contemporaneous agreements
or understandings, whether written or oral, with respect to the subject matter
hereof. No amendment or modification hereto shall be valid unless in writing and
signed by both parties hereto.

                               XVII. SEVERABILITY

If any provision of this Agreement, or any amendment thereof, should be invalid,
the remaining provision shall remain in effect and be so construed as to
effectuate the intent and purposes of this Agreement and any amendments thereto.

                                XVIII. NOTICES

All notices, requests and communications provided hereunder shall be in writing,
and hand delivered or mailed by United States registered, certified, or express
mail, return receipt requested, and addressed to the party's principal place of
business as set forth in this Agreement adjacent the signature of each party (or
to such other address provided in writing by such party).

                                   XIX. WAIVER

The waiver by either party hereto of a breach of any term or provision of this
Agreement shall not operate or be construed as a waiver of a subsequent breach
of the same provision by any party or of a breach of any other term or provision
of this Agreement.

                                  XX. EXHIBITS

The following exhibits are attached to this Agreement and incorporated herein by
reference for all purposes:

A.    Exhibit A ("Confidential Census");




                                        5


<PAGE>   14

B.    Exhibit B ("Client Service Application"); and,

C.    Exhibit C ("Employment Agreement Form").

THIS AGREEMENT is duly executed this 30 day of June, 1996.
                                    ----       -----    -
FOR CLIENT:  MHM of Colorado, Inc.         
             -----------------------       ADMINISTAFF COMPANIES, INC.
                (Company Name)             19001 Crescent Springs Drive
                                           Kingwood, Texas 77339-3802
                                           (713) 358-8986

By: /s/ MICHAEL PINKERT                    By:   /s/ A. STEVE ARIZOF
    ---------------------------------          ---------------------------------
    (Signature)             President                            Vice-President
        Michael Pinkert
    ---------------------------------
    (Name - Typed or Printed)

Address:  4601 Corbett Dr.
          ---------------------------
          Ft Collins, Co  80525
          ---------------------------

          ---------------------------

Tel. No.: (970) 225-9191
          ---------------------------