Document:

<PAGE>   1
                                                                   EXHIBIT 10.12

                              EMPLOYMENT AGREEMENT

         This Employment Agreement (this "Agreement") is made and entered into
as of the 12th day of January 2001 by and between MAII Holdings, Inc., a Texas
corporation ("Employer"), and Christie S. Tyler ("Employee").

                                  WITNESSETH:

         WHEREAS, Employer desires to employ Employee as provided herein, and
Employee desires to accept such employment; and

         WHEREAS, Employee shall, as an employee of Employer, have access to
confidential information with respect to Employer and its affiliates;

         NOW THEREFORE, for and in consideration of the mutual covenants and
agreements contained herein, and for other good and valuable consideration, the
receipt and sufficiency of which is hereby acknowledged, the parties hereto
agree as follows:

         1. Employment. Employer hereby employs Employee and Employee hereby
accepts employment with Employer upon the terms and conditions set forth in this
Agreement.

         2. Duties. Employee shall serve Employer as the Chief Executive
Officer, and shall perform, faithfully and diligently, the services and
functions relating to such office or otherwise reasonably incident to such
office as may be designated from time to time by the board of directors.
Employee shall be based in Dallas, Texas, but shall have duties and
responsibilities at and/or with respect to each location at which Employer or
any of its affiliates conducts the Business (as defined in Section 5(d)) and
shall travel as reasonably required by Employee's duties under this Agreement.
Employee shall devote Employee's full business time, attention, energies and
business efforts to Employee's duties hereunder and to the promotion of the
business and interests of Employer and its affiliates.

         3. Term. The term of this Agreement shall commence as of the date
hereof and shall continue, unless earlier terminated pursuant to Section 7
below, for a period of three (3) years thereafter (the "Term"); provided,
however, that the Term may be extended upon the mutual written agreement of
Employer and Employee.

         4. Compensation. As compensation for his services rendered under this
Agreement, during the Term Employee shall be entitled to receive the following:

            (a) Salary. Employer shall, subject to the terms and conditions
hereof, pay Employee an initial annual salary of $300,000 per year, which shall
increase to $400,000 per year at the date Employer completes the acquisition of
an operating company or consummates public or private offerings aggregating at
least $15,000,000 (the "Salary"). The Salary shall be payable in arrears and in
equal monthly installments.

            (b) Bonus. Employee shall be entitled to receive bonuses, if any, as
may be awarded to Employee by the Board of Directors of Employer (the "Board").

                                       1
<PAGE>   2

            (c) Stock Options. Employer shall execute and deliver to Employee
two Non-Qualified Stock Option Agreements, the forms of which are attached
hereto as Exhibit A and Exhibit B; and

            (d) Employee Benefit Plans. Employer shall pay to Employee $300 per
month for health insurance to be purchased by Employee until such time as
Employer adopts a health insurance plan and Employer receives coverage
thereunder, at which time Employer shall no longer be entitled to receive such
monthly payments. Employee shall, on terms no less favorable to Employee than
any other senior executive of Employer, have the right to become a participant
or beneficiary under or pursuant to any and all employee benefit plans adopted
and maintained from time to time by the Company and for which Employee is
eligible under the respective provisions thereof. Nothing in this Agreement
shall require Employer to adopt any employee benefit plan and nothing in this
Agreement shall prevent Employer from amending, modifying or terminating any or
all employee benefit plans now or hereafter in force.

            (e) Business Expenses. Employee shall be entitled to reimbursement
for all business, travel and other out-of-pocket expenses reasonably incurred by
Employee in the performance of his duties pursuant to this Agreement and in
accordance with any policies established by Employer. All such expenses shall be
appropriately documented in reasonable detail by Employee upon submission of any
request for reimbursement.

         5. Confidentiality.

            (a) Acknowledgment of Proprietary Interest. Employee recognizes the
proprietary interest of Employer and its affiliates in any Trade Secrets (as
defined below) of Employer and its affiliates. Employee acknowledges and agrees
that any and all Trade Secrets currently known by Employee or learned by
Employee during the course of his engagement by Employer or otherwise, whether
developed by Employee alone or in conjunction with others or otherwise, shall be
and are the property of Employer and its affiliates. Employee further
acknowledges and understands that his disclosure of any Trade Secrets may result
in irreparable injury and damage to Employer and its affiliates. As used herein,
"Trade Secrets" means all confidential and proprietary information of Employer
and its affiliates, now owned or hereafter acquired, including, without
limitation, information derived from reports, investigations, experiments,
research, work in progress, drawing, designs, plans, proposals, codes, marketing
and sales programs, client lists, client mailing lists, financial projections,
cost summaries, pricing formula, and all other concepts, ideas, materials, or
information prepared or performed for or by Employer or its affiliates and
information related to the business, products or sales of Employer or its
affiliates, or any of their respective customers, other than information which
is otherwise publicly available.

            (b) Covenant Not-to-Divulge Trade Secrets. Employee acknowledges and
agrees that Employer and its affiliates are entitled to prevent the disclosure
of Trade Secrets. As a portion of the consideration for the employment of
Employee and for the compensation being paid to Employee by Employer, Employee
agrees at all times during the Term and for a period of five (5) years
thereafter to hold in strict confidence and not to intentionally disclose
(except for such disclosures as are required by law, in which case, Employee
agrees to give Employer notice thereof prior to making any such disclosure) or
allow to be disclosed to any person, firm or

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<PAGE>   3

corporation, other than to persons engaged by Employer and its affiliates to
further the business of Employer and its affiliates, and not to use except in
the pursuit of the business of Employer and its affiliates, the Trade Secrets,
without the prior written consent of Employer, including Trade Secrets developed
by Employee.

            (c) Return of Materials at Termination. In the event of any
termination or cessation of his employment with Employer for any reason
whatsoever, Employee will promptly deliver to Employer all documents, data and
other information pertaining to Trade Secrets. Employee shall not take any
documents or other information, of whatever type and in whatever form, or any
reproduction or excerpt thereof, containing or pertaining to any Trade Secrets.

            (d) Competition During and After Employment. Employee agrees that
during the Term and for a period of one year thereafter, neither Employee, nor
any of his affiliates, will directly or indirectly act as an investor,
principal, member, partner, officer, director, employee, consultant,
shareholder, lender, or agent of any entity which is engaged in any business of
the same nature as, or in competition with, the business conducted by Employer
and its affiliates during the Term (the "Business") within North America.

         6. Prohibition on Disparaging Remarks. Employee shall, from the date of
this Agreement forward, refrain from making disparaging, negative or other
similar remarks concerning Employer or any of its affiliates to any third party.
Similarly, Employer and its affiliates shall from the date of this Agreement
forward, refrain from making disparaging, negative or other similar remarks
concerning Employee to any third party.

         7. Termination.

            (a) This Agreement and the employment relationship created hereby
shall terminate upon the occurrence of any of the following events (each, a
"Termination Event"):

               (i)   The expiration of the Term;

               (ii)  The death of Employee;

               (iii) The Disability (as hereinafter defined) of Employee;

               (iv)  Written notice to Employee from Employer of termination for
          Just Cause (as defined below);

               (v)   Written notice to Employee from Employer of termination for
          any reason other than Just Cause;

               (vi)  Written notice to Employer from Employee of termination for
          Good Reason (as defined below); or

               (vii) Written notice to Employer from Employee of termination for
          any reason other than Good Reason.

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<PAGE>   4
         (b) Payments Upon Termination.

               (i) If this Agreement is terminated pursuant to 7(a)(i),
          7(a)(ii), 7(a)(iii), 7(a)(iv), or 7(a)(vii), then Employer shall have
          no obligation to pay to Employee the Salary or any other compensation
          or benefits provided under this Agreement for any period after the
          date of such termination, provided, however, that Employer shall pay
          to Employee all Salary and other compensation and vested benefits
          accrued but unpaid prior to the date of such termination.

               (ii) If this Agreement is terminated pursuant to Section 7(a)(v)
          or 7(a)(vi), then, in addition to the Salary earned by Employee prior
          to the date of such termination, Employer shall pay Employee a
          severance payment in an amount equal to the monthly installment of
          Employee's Salary then in effect multiplied by the remaining months of
          the Term; provided, however, if termination occurs on or prior to July
          12, 2001, then such period shall only be six months and not the
          remaining months of the Term. Any such severance payment shall be paid
          by Employer, at its option, either (i) in accordance with Employer's
          regular payroll practices, or (ii) a lump sum payment equal to the
          present value, based on a discount rate equal to the prime rate of
          Chase Manhattan Bank then in effect, of the total amount specified.

         (c) For purposes of this Section 7 the following terms have the
following meanings:

          "Disability" of Employee shall mean Employee's inability, because of
     mental or physical illness or incapacity, to perform Employee's duties
     under this Agreement for a continuous period of 90 consecutive days or for
     any 120 days out of a 360-day period. In the event of any disagreement
     between Employer and Employee regarding the existence or non-existence of
     any such disability, upon written request from either party to the other,
     Employer and Employee or Employee's legal guardian or duly authorized
     attorney-in-fact (if Employee is not legally competent) shall each
     designate one Texas licensed physician and the two physicians so designated
     shall designate a third. All three physicians so appointed shall personally
     examine Employee, and the decision of a majority of such panel of
     physicians shall determine whether such disability exists. Employee hereby
     authorizes the disclosure and release to Employer of such determination and
     all supporting medical records, and both parties hereby agree to be bound
     by such determination.

          "Good Reason" shall mean: (a) a breach by Employer of a material terms
     of, or the failure to perform any material covenant contained in, this
     Agreement and following written notice thereof from Employee to Employer,
     Employer does not cure such breach or failure within fifteen (15) days
     thereafter; provided, however, that Employer will not be entitled to cure
     any breach or failure of this subclause (a) more than one time in any three
     month period; (b) a material reduction in Employee's compensation, duties,
     authority and/or responsibilities without Employee's consent; or (c)
     conviction of Employer for a felony related to activities in which Employee
     has not participated.

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<PAGE>   5
               "Just Cause" shall mean: (a) the commission by Employee of any
          act or the suffering by Employee of any occurrence or state of facts,
          which renders Employee incapable of performing Employee's duties under
          this Agreement (other than Disability), or adversely affects or could
          be expected to adversely affect Employer's business reputation; (b)
          Employee's being convicted of a felony; (c) any breach by Employee of
          any of the material terms of, or the failure to perform any material
          covenant contained in, this Agreement and following written notice
          thereof from Employer to Employee, Employee does not cure such breach
          or failure within fifteen (15) days thereafter; provided, however,
          that Employee will not be entitled to cure any breach or failure under
          this subclause (c) more than one time in any consecutive three month
          period; (d) the violation by Employee of reasonable and appropriate
          instructions or policies established by the board of directors which
          have been communicated to Employee with respect to the operation of
          the businesses and affairs of Employer or Employee's failure to carry
          out the reasonable instructions of the Board of Directors of Employer
          and following written notice thereof, Employee does not cure any such
          violation or failure within fifteen (15) days thereafter; provided,
          however, that Employee will not be entitled to cure any violation or
          failure under this subclause (d) more than one time in any consecutive
          three month period; or (e) if Employee fails to pay off in full all
          principal of and interest on that certain Promissory Note, to be dated
          February 1, 2001, by and between Employer and Employee, and in the
          original principal amount of $2,739,040.

         8. Remedies. Employee recognizes and acknowledges that in the event of
any default in, or breach of any of, the terms, conditions or provisions of this
Agreement (either actual or threatened) by Employee, Employer's and its
affiliates remedies at law shall be inadequate. Accordingly, Employee agrees
that in such event, Employer and its affiliates shall have the right of specific
performance and/or injunctive relief in addition to any and all other remedies
and rights at law, in equity or provided herein, and such rights and remedies
shall be cumulative.

         9. Acknowledgments. Employee acknowledges and recognizes that the
enforcement of any of the provisions set forth in Section 5 and 6 above by
Employer and its affiliates will not interfere with Employee's ability to pursue
a proper livelihood. Employee recognizes and agrees that the enforcement of this
Agreement is necessary to ensure the preservation and continuity of the business
and good will of Employer and its affiliates.

         10. Notices. Any notices, consents, demands, requests, approvals and
other communications to be given under this Agreement by either party to the
other shall be deemed to have been duly given if given in writing and personally
delivered or sent by facsimile transmission, courier service, overnight delivery
service or by mail, registered or certified, postage prepaid with return receipt
requested, as follows:

         If to Employer:          MAII Holdings, Inc.
                                  c/o Richard F. Dahlson, Esq.
                                  Jackson Walker L.L.P.
                                  901 Main Street, Suite 6000
                                  Dallas, Texas  75202
                                  Attn:  Board of Directors

                                       5
<PAGE>   6
         If to Employee:          Christie S. Tyler
                                  5823 Encore Drive
                                  Dallas, Texas  75240

         Notices delivered personally or by facsimile transmission, courier
service or overnight delivery shall be deemed communicated as of actual receipt;
mailed notices shall be deemed communicated as of three days after the date of
mailing.

         11. Entire Agreement. This Agreement, including Exhibit A and Exhibit B
attached hereto, contains the entire agreement of the parties hereto with
respect to the subject matter hereof and supersedes all prior agreements and
understandings, oral or written between the parties hereto with respect hereto.
No modification or amendment of any of the terms, conditions or provisions
herein may be made otherwise than by written agreement signed by the parties
hereto.

         12. Governing Law and Venue. THE RIGHTS AND OBLIGATIONS OF THE PARTIES
HEREUNDER SHALL BE INTERPRETED, CONSTRUED, AND ENFORCED IN ACCORDANCE WITH THE
LAWS OF THE STATE OF TEXAS, WITHOUT REGARD TO ITS CHOICE OF LAW PRINCIPLES. ANY
ACTION BROUGHT BY EITHER PARTY HERETO INVOLVING ENFORCEMENT, TERMINATION,
INTERPRETATION, OR MODIFICATION HEREOF, OR OTHERWISE RELATED TO THIS AGREEMENTS
IN ANY WAY SHALL BE BROUGHT IN A COURT LOCATED IN DALLAS, TEXAS, AND NEITHER
PARTY HERETO SHALL BE HEARD TO ASSERT THE DEFENSE OF INCONVENIENT FORUM IN ANY
SUCH ACTION.

         13. Parties Bound. This Agreement and the rights and obligations
hereunder shall be binding upon and inure to the benefit of Employer and
Employee, and their respective heirs, personal representatives, successors and
assigns. Employer shall have the right to assign this Agreement to any affiliate
or to its successors or assigns. The terms "successors" and "assigns" shall
include any person, corporation, partnership or other entity that buys all or
substantially all of Employer's assets or all of its stock, or with which
Employer merges or consolidates. The rights, duties or benefits to Employee
hereunder are personal to him, and no such right, duty or benefit may be
assigned by Employee; provided, however, that the economic benefits of this
Agreement may be assigned by Employee to a personal corporation of Employee. The
parties hereto acknowledge and agree that Employer's affiliates are third-party
beneficiaries of the covenants and agreements of Employee set forth in Sections
5 and 6 above.

         14. Arbitration. Any dispute or claim arising under or with respect to
this Agreement shall be settled by arbitration in Dallas, Texas, pursuant to the
rules and guidelines of the American Arbitration Association - Commercial
Division. The decision of the arbitrators shall be final and binding upon
Employer and Employee, and any decision or award rendered by the arbitrators may
be entered as a judgment or order in any court having jurisdiction.

         15. Estate. If Employee dies prior to the payment of all sums owed, or
to be owed, to Employee pursuant to Section 4 above, then such sums, as they
become due, shall be paid to Employee's estate.

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<PAGE>   7
         16. Enforceability. If, for any reason, any provision contained in this
Agreement should be held invalid in part by a court of competent jurisdiction,
then it is the intent of each of the parties hereto that the balance of this
Agreement be enforced to the fullest extent permitted by applicable law.
Accordingly, should a court of competent jurisdiction determine that the scope
of any covenant is too broad to be enforced as written, it is the intent of each
of the parties that the court should reform such covenant to such narrower scope
as it determines enforceable.

         17. Waiver of Breach. The waiver by any party hereto of a breach of any
provision of this Agreement shall not operate or be construed as a waiver of any
subsequent breach by any party.

         18. Captions. The captions in this Agreement are for convenience of
reference only and shall not limit or otherwise affect any of the terms or
provisions hereof.

         19. Costs. If any action at law or in equity, or by reason of Section
14 above, is necessary to enforce or interpret the terms of this Agreement, the
prevailing party shall be entitled to reasonable attorneys' fees, costs and
necessary disbursements in addition to any other relief to which he or it may be
entitled.

         20. Other Obligations. Employee represents and warrants that Employee
is not subject to any agreement which would be violated or breached as a direct
or indirect result of Employee executing this Agreement or Employee becoming an
employee of Employer.

         21. Affiliate; Subsidiary. An "affiliate" of any party hereto shall
mean any person controlling, controlled by or under common control with such
party. A "subsidiary" of Employer is any partnership, corporation, limited
liability company or other entity in which Employer owns an equity interest. For
purposes of this Agreement, the term "control", when used with respect to any
specified person or entity means the power to direct or cause the direction of
the management and policies of such person or entity, directly or indirectly,
whether through the ownership of voting securities of ten percent (10%) or more,
by contract, or otherwise, and the term "controlled" has the meaning correlative
to the foregoing.

         22. Notwithstanding anything to the contrary in this Agreement, the
provisions of Sections 5 and 6 above shall survive any termination, for whatever
reason, of Employee's employment under this Agreement.

         23. Counterparts. This Agreement may be executed in one or more
counterparts, each of which shall be deemed an original and all of which shall
constitute one and the same instrument, but only one of which need be produced.

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<PAGE>   8
         IN WITNESS WHEREOF, the parties hereto have duly executed this
Agreement as of the day and year first above written.

                               MAII HOLDINGS, INC.

                               By: /s/ RICHARD F. DAHLSON
                                  ---------------------------------------------
                               Name: Richard F. Dahlson
                                    -------------------------------------------
                               Its:  Director
                                   --------------------------------------------

                               EMPLOYEE:

                                /s/ CHRISTIE S. TYLER
                               -------------------------------------------------
                                    Christie S. Tyler

                                       8
<PAGE>   9
                                    EXHIBIT A

                      Non-Qualified Stock Option Agreement

                                      A-1
<PAGE>   10
                               MAII HOLDINGS, INC.
                      NON-QUALIFIED STOCK OPTION AGREEMENT

         This Non-Qualified Stock Option Agreement (the "Agreement") is entered
into between MAII Holdings, Inc., a Texas corporation (the "Company"), and
Christie S. Tyler (the "Optionee") as of the 12th day of January, 2001. In
consideration of the mutual promises and covenants made herein, the parties
hereby agree as follows:

         1. GRANT OF OPTION. Under the terms and conditions of the Company's
Amended and Restated 1994 Long-Term Incentive Plan (the "Plan"), a copy of which
is attached hereto and incorporated herein by reference, the Company grants to
the Optionee an option (the "Option") to purchase from the Company all or any
part of a total of One Hundred Sixty-Six Thousand Six Hundred Sixty-Seven
(166,667) shares of the Company's Common Stock, par value $.002 per share, at a
price of $4.03 per share. The Option is granted as of January 12, 2001 (the
"Date of Grant").

         2. CHARACTER OF OPTION. The Option is not an "incentive stock option"
within the meaning of Section 422 of the Internal Revenue Code of 1986, as
amended (the "Code").

         3. TERM. The Option will expire on the day prior to the fifth
anniversary of the Date of Grant or, in the event of the Optionee's termination
of service as an Employee of the Company, on such earlier date as may be
provided in Section 4.8(a) of the Plan.

         4. VESTING. The Option may be exercised, in whole or in part, at any
time from and after the Date of Grant on the following schedule.

<TABLE>
<CAPTION>
                 Cumulative Amount of Shares
                   Exercisable (Vested)                       Period
                   --------------------                       ------
<S>                                                     <C>
                           33,333                       On or after April 12, 2001
                           66,666                       On or after July 12, 2001
                           99,999                       On or after October 12, 2001
                          133,332                       On or after January 1, 2002
                          166,667                       On or after April 12, 2002
</TABLE>

         The unexercised vested portion of the Option from one period may be
carried over to a subsequent period or periods, and the right of the Optionee to
exercise the Option as to such unexercised vested portion shall continue for the
entire term.

         5. PROCEDURE FOR EXERCISE. Exercise of the Option or a portion thereof
shall be effected by the giving of written notice to the Company by the Optionee
in accordance with Section 4.7 of the Plan and payment of the purchase price
prescribed in Section 1 above for the shares to be acquired pursuant to the
exercise.

         6. PAYMENT OF PURCHASE PRICE. Payment of the purchase price for any
shares purchased pursuant to the Option shall be in accordance with the
provisions of Section 4.7 of the Plan.

<PAGE>   11

         7. TRANSFER OF OPTIONS. The Option may not be transferred except (i) by
will or the laws of descent and distribution or (ii) pursuant to the terms of a
qualified domestic relations order, as defined by the Code or Title I of the
Employee Retirement Income Security Act of 1974, as amended, and, during the
lifetime of the Optionee, may be exercised only by the Optionee or by the
Optionee's legally authorized representative.

         8. ACCEPTANCE OF THE PLAN. The Option is granted subject to all of the
applicable terms and provisions of the Plan, and such terms and provisions are
incorporated by reference herein. The Optionee hereby accepts and agrees to be
bound by all the terms and conditions of the Plan.

         9. AMENDMENT. This Agreement may be amended by an instrument in writing
signed by both the Company and the Optionee.

         10. MISCELLANEOUS. This Agreement will be construed and enforced in
accordance with the laws of the State of Texas and will be binding upon and
inure to the benefit of any successor or assign of the Company and any executor,
administrator, trustee, guarantor or other legal representative of the Optionee.

         Executed as of the 12th day of January, 2001.

                               THE COMPANY:

                               MAII HOLDINGS, INC.

                               By: /s/ RICHARD F. DAHLSON
                                  ---------------------------------------------
                               Name: Richard F. Dahlson
                                    -------------------------------------------
                               Its:  Director
                                   --------------------------------------------

                               THE OPTIONEE:

                               /s/ CHRISTIE S. TYLER
                               ------------------------------------------------
                               Christie S. Tyler
                               Social Security Number of Optionee:  ###-##-####

         Exhibit: The Plan

<PAGE>   12

                                    EXHIBIT B

                      Non-Qualified Stock Option Agreement

                                       B-1
<PAGE>   13

                               MAII HOLDINGS, INC.
                      NON-QUALIFIED STOCK OPTION AGREEMENT

         This Non-Qualified Stock Option Agreement (the "Agreement") is entered
into between MAII Holdings, Inc., a Texas corporation (the "Company"), and
Christie S. Tyler (the "Optionee") as of the 12th day of January, 2001. In
consideration of the mutual promises and covenants made herein, the parties
hereby agree as follows:

         1. GRANT OF OPTION. Under the terms and conditions of the Company's
Amended and Restated 1994 Long-Term Incentive Plan (the "Plan"), a copy of which
is attached hereto and incorporated herein by reference, the Company grants to
the Optionee an option (the "Option") to purchase from the Company all or any
part of a total of Two Hundred Thirty-Three Thousand Three Hundred Thirty-Three
(233,333) shares of the Company's Common Stock, par value $.002 per share, at a
price of $4.03 per share. The Option is granted as of January 12, 2001 (the
"Date of Grant"). Notwithstanding anything in this Agreement to the contrary,
this Agreement and the Option, including without limitation, the granting and
vesting thereof, shall be subject to the approval by the shareholders of the
Company of an amendment to the Plan which increases the number of shares of
Stock (as defined in the Plan) to at least 2,000,000 shares from the current
1,624,290 shares, and if such approval is not received, this Agreement and the
Option shall be considered null and void.

         2. CHARACTER OF OPTION. The Option is not an "incentive stock option"
within the meaning of Section 422 of the Internal Revenue Code of 1986, as
amended (the "Code").

         3. TERM. The Option will expire on the day prior to the fifth
anniversary of the Date of Grant or, in the event of the Optionee's termination
of service as an Employee of the Company, on such earlier date as may be
provided in Section 4.8(a) of the Plan.

         4. VESTING. The Option may be exercised, in whole or in part, at any
time from and after the Date of Grant on the following schedule.

<TABLE>
<CAPTION>
                 Cumulative Amount of Shares
                 Exercisable (Vested)                         Period
                 --------------------                         ------
<S>                                                    <C>
                           33,333                      After July 12, 2002
                           66,666                      On or after October 12, 2002
                           99,999                      On or after January 12, 2003
                          133,332                      On or after April 12, 2003
                          166,665                      On or after July 12, 2003
                          199,998                      On or after October 12, 2003
                          233,333                      On or after January 12, 2004
</TABLE>

         The unexercised vested portion of the Option from one period may be
carried over to a subsequent period or periods, and the right of the Optionee to
exercise the Option as to such unexercised vested portion shall continue for the
entire term.

<PAGE>   14

         5. PROCEDURE FOR EXERCISE. Exercise of the Option or a portion thereof
shall be effected by the giving of written notice to the Company by the Optionee
in accordance with Section 4.7 of the Plan and payment of the purchase price
prescribed in Section 1 above for the shares to be acquired pursuant to the
exercise.

         6. PAYMENT OF PURCHASE PRICE. Payment of the purchase price for any
shares purchased pursuant to the Option shall be in accordance with the
provisions of Section 4.7 of the Plan.

         7. TRANSFER OF OPTIONS. The Option may not be transferred except (i) by
will or the laws of descent and distribution or (ii) pursuant to the terms of a
qualified domestic relations order, as defined by the Code or Title I of the
Employee Retirement Income Security Act of 1974, as amended, and, during the
lifetime of the Optionee, may be exercised only by the Optionee or by the
Optionee's legally authorized representative.

         8. ACCEPTANCE OF THE PLAN. The Option is granted subject to all of the
applicable terms and provisions of the Plan, and such terms and provisions are
incorporated by reference herein. The Optionee hereby accepts and agrees to be
bound by all the terms and conditions of the Plan.

         9. AMENDMENT. This Agreement may be amended by an instrument in writing
signed by both the Company and the Optionee.

         10. MISCELLANEOUS. This Agreement will be construed and enforced in
accordance with the laws of the State of Texas and will be binding upon and
inure to the benefit of any successor or assign of the Company and any executor,
administrator, trustee, guarantor or other legal representative of the Optionee.

         Executed as of the 12th day of January, 2001.

                               THE COMPANY:

                               MAII HOLDINGS, INC.

                               By: /s/ RICHARD F. DAHLSON
                                  ---------------------------------------------
                               Name: Richard F. Dahlson
                                    -------------------------------------------
                               Its:  Director
                                   --------------------------------------------

                               THE OPTIONEE:

                               /s/ CHRISTIE S. TYLER
                               ------------------------------------------------
                               Christie S. Tyler
                               Social Security Number of Optionee:  ###-##-####

         Exhibit: The Plan<PAGE>   1
                                                                   EXHIBIT 10.13

                            STOCK PURCHASE AGREEMENT

         This Stock Purchase Agreement (the "Agreement") is entered into by and
between MAII Holdings, Inc., a Texas corporation (the "Corporation"), and
Christie S. Tyler ("Tyler"), as of February 1, 2001.

                                     RECITAL

         To provide incentive for Tyler to serve as the chief executive officer
of the Corporation, the Corporation desires to issue to Tyler, and Tyler desires
to purchase from the Corporation, 680,000 shares of the common stock, par value
$0.002 per share (the "Common Stock"), of the Corporation on the terms and
conditions set forth in this Agreement.

         1. Issuance of Shares. The Corporation hereby issues to Tyler in
exchange for the Purchase Price, 680,000 shares of Common Stock (the "Shares").
The purchase price of the Shares is $4.03 per Share, for a total purchase price
of $2,740,400 (the "Purchase Price"). The Purchase Price shall be paid
simultaneously with the execution of this Agreement by the parties hereto. Tyler
shall pay the Purchase Price by delivering to the Corporation (i) $1,360 in
cash; and (ii) a promissory note in the original principal amount of $2,739,040,
and in the form attached hereto as Exhibit A and incorporated by reference
herein (the "Note"). The Note shall be secured by a security interest in the
Shares pursuant to a Pledge and Security Agreement in the form attached hereto
as Exhibit B and incorporated by reference herein.

         2. Delivery of Certificates. Simultaneously with the execution of this
Agreement, the Corporation shall deliver to Tyler certificates evidencing the
Shares. The Shares for all purposes shall be considered issued on the date of
this Agreement.

         3. Put by Tyler. The parties hereto acknowledge and agree that Tyler
may, on or prior to April 12, 2001, purchase shares of Common Stock from current
shareholders of the Corporation. To the extent that Tyler does so, Tyler may, on
or prior to April 12, 2001, sell to the Corporation, for the price of $4.03 per
share, that number of Shares equal to the number of shares of Common Stock which
Tyler purchased from shareholders of the Company. The option granted Tyler
pursuant to this Section 3 (the "Put") shall be exercised by Tyler delivering
written notice of his intent to exercise to the Corporation at the address set
forth in Section 4, on or prior to April 12, 2001. Such notice shall specify the
number of shares to be sold to the Corporation. Such sale and purchase shall be
closed at a time and place agreeable to the parties no later than 15 days after
receipt by the Corporation of such notice. Notwithstanding anything contained
herein, the price to be paid by the Corporation upon exercise of the Put, shall
first be applied to the outstanding balance of unpaid accrued interest and
principal on the Note, and the balance, if any, shall be paid to Tyler in cash.
The Put shall apply only to the Shares and no other shares of common stock of
the Corporation, and may not be transferred or assigned by Tyler. No holder of
the Shares, other than Tyler, may exercise the Put.

         4. Notices. All notices required or permitted hereunder shall be in
writing and shall be deemed to be delivered when delivered in person, or when
deposited in the United States mail, postage prepaid, registered or certified
mail, return receipt requested, addressed as follows:

<PAGE>   2
         If to Tyler:                        Christie S. Tyler
                                             5823 Encore Drive
                                             Dallas, Texas  75240

         If to the Corporation:              MAII Holdings, Inc.
                                             c/o Jackson Walker L.L.P.
                                             901 Main Street Suite 6000
                                             Dallas, Texas  75202
                                             Attn:  Richard F. Dahlson

         5. Entire Agreement. This Agreement contains the entire agreement
between the parties with respect to the subject matter hereof and supersedes all
prior agreements, understandings and statements, written or oral, with respect
thereto.

         6. Severability. In the event that one or more of the provisions of
this Agreement shall, for any reason, be held to be invalid, illegal or
unenforceable in any respect, such invalid, illegal or unenforceable provision
shall not affect any other provision hereof, and this Agreement shall be
construed as if such invalid, illegal, or unenforceable provision had never been
contained herein.

         7. Further Assurances. Tyler and the Corporation agree to take all
actions reasonably necessary to effectuate the intents and purposes of this
Agreement.

         8. Texas Law to Apply. This Agreement shall be construed under and in
accordance with the laws of the State of Texas, and all obligations of the
parties created hereunder are performable in Dallas County, Texas.

         9. Headings. The headings used in this Agreement are used for
administrative purposes only and do not constitute substantive matter to be
considered in construing the terms of this Agreement.

         10. Parties Bound. This Agreement shall be binding upon and shall inure
to the benefit of the parties hereto and to the extent permitted by this
Agreement, their successors and assigns.

         11. Amendment. This Agreement may be amended or modified only by a
writing executed by the parties.

         12. Waiver. No term or condition of this Agreement shall be deemed to
have been waived by a party, nor shall there be any estoppel against the
enforcement by a party of any provisions of this Agreement, except by written
instrument executed by the other party. No such written waiver by a party shall
be deemed a continuing waiver unless specifically stated therein, and each such
waiver shall operate only as to the specific terms or conditions waived and
shall not constitute a waiver of such terms or conditions for the future or as
to any act other than that specifically waived.

                                       2
<PAGE>   3
         13. Counterparts. This Agreement may be executed in multiple
counterparts all of which shall constitute one agreement and each of which shall
constitute an original of this Agreement.

         Dated as of the date first written above.

                                   MAII HOLDINGS, INC.

                                   By: /s/ RICHARD F. DAHLSON
                                      ------------------------------------------
                                   Its: Director
                                       -----------------------------------------

                                    /s/ CHRISTIE S. TYLER
                                   ---------------------------------------------
                                       Christie S. Tyler

                                       3

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