<PAGE>
                                                                   Exhibit 10.18

                       FIRST AMENDMENT TO CREDIT AGREEMENT

         THIS FIRST AMENDMENT TO CREDIT AGREEMENT dated effective as of January
24, 2003 (the "FIRST AMENDMENT" or this "AMENDMENT") is among NELNET LOAN
SERVICES, INC., a corporation duly organized and validly existing under the laws
of the State of Nebraska ("NLSI"), NELNET, INC., a corporation duly organized
and validly existing under the laws of the State of Nevada ("NELNET" and NLSI,
herein each individually a "BORROWER" and collectively "BORROWERS"), and BANK OF
AMERICA, N.A., a national banking association ("BANK").

                              PRELIMINARY STATEMENT

         (1)      Pursuant to that certain Credit Agreement dated as of January
11, 2002, among Borrowers and Bank, Bank made a revolving credit facility
available to Borrowers upon the terms and conditions set forth therein (the
"CREDIT AGREEMENT").

         (2)      Borrowers have requested that the Credit Agreement be renewed,
amended, and extended, and Bank has agreed to renew, extend, and amend the
Credit Agreement to the extent and in the manner set forth herein.

         Accordingly, in consideration of the foregoing and the mutual covenants
set forth herein, the parties hereto agree as follows:

                                    ARTICLE I
                                   DEFINITIONS

         SECTION 1.01      DEFINED TERMS. All capitalized terms defined in the
Credit Agreement, and not otherwise defined herein shall have the same meanings
herein as in the Credit Agreement. Upon the effectiveness of this Amendment,
each reference (a) in the Credit Agreement to "this Agreement," "hereunder,"
"herein" or words of like import shall mean and be a reference to the Credit
Agreement, as amended hereby, (b) in the Note and the other Loan Documents to
the Credit Agreement shall mean and be a reference to the Credit Agreement, as
amended hereby, and (c) in the Loan Documents to any term defined by reference
to the Credit Agreement shall mean and be a reference to such term as defined in
the Credit Agreement, as amended hereby.

         SECTION 1.02      REFERENCES, ETC. The words "hereof," "herein" and
"hereunder" and words of similar import when used in this Amendment shall refer
to this Amendment as a whole and not to any particular provision of this
Amendment. In this Amendment, unless a clear contrary intention appears the word
"including" (and with correlative meaning "include") means including, without
limiting the generality of any description preceding such term. No provision of
this Amendment shall be interpreted or constructed against any Person solely
because that Person or its legal representative drafted such provision.

                                                                 FIRST AMENDMENT

<PAGE>

                                   ARTICLE II
                         AMENDMENTS TO CREDIT AGREEMENT

         SECTION 2.01      AMENDMENTS TO SECTION 1.1.

             (a)  SECTION 1.1 of the Credit Agreement is hereby amended by
         deleting the definitions of "Advance Termination Date," "Fixed
         Charges," "Maturity Date," and "Permitted Debt" and substituting the
         following definitions in lieu thereof:

                  "ADVANCE TERMINATION DATE" means January 23, 2004.

                  "FIXED CHARGES" means, for any period, the sum of following
                  calculated for Borrowers and their respective Subsidiaries on
                  a consolidated basis without duplication: (i) pro forma
                  interest expense relating to Permitted Debt; plus (ii)
                  Commercial Paper Debt and that portion of the long term Debt
                  that should be classified as current in accordance with GAAP
                  as of the first day of such period but excluding, to the
                  extent included, the outstanding principal amount of Permitted
                  Debt and any Debt to be assumed in connection with a Proposed
                  Acquisition; plus (iii) (a) .25 multiplied by (b) the sum of
                  (1) the principal amount of the Permitted Debt outstanding on
                  the date of determination (which has not been included in (ii)
                  above) plus (2) the amount of the Loan requested plus (3) the
                  principal amount of the Debt to be assumed in connection with
                  a Proposed Acquisition. Pro forma interest expense shall be
                  determined in good faith by a financial officer of Borrower
                  and when calculating pro forma interest expense with respect
                  to any Debt bearing interest at a floating rate, the interest
                  expense on such Debt shall be calculated at the average
                  interest rate applicable to the Loans in the immediately
                  preceding fiscal quarter for the entire period and as if the
                  accrued interest thereon is payable as of the end of each
                  fiscal quarter.

                  "MATURITY DATE" means January 23, 2005.

                  "PERMITTED DEBT" means Debt described in Section 8.1(a), (b),
                  (i), (j), (k) and (l) and the SLIMS.

             (b)  SECTION 1.1 is hereby amended by adding the following
             definition thereto:

                  "COMMERCIAL PAPER DEBT" means up to (a) $50,000,000 aggregate
                  principal amount or such other amount as agreed upon in
                  writing by Borrowers and the Bank of unsecured commercial
                  paper issued by either or both Borrowers, and (b) any loan
                  facility on terms and conditions reasonably acceptable to Bank
                  whose sole use of proceeds is to fund, when due, any payment
                  of commercial paper.

                                                                 FIRST AMENDMENT

                                        2

<PAGE>

         SECTION 2.02      AMENDMENT TO SECTION 2.3(a). SECTION 2.3(a) of the
Credit Agreement is hereby deleted and the following new SECTION 2.3(a) is
substituted in lieu thereof:

                  (a)      Three (3) quarterly principal installments due and
                  payable on March 31, 2004, June 30, 2004 and September 30,
                  2004, each installment in an aggregate principal amount equal
                  to the quotient obtained by dividing the aggregate principal
                  amount of the Loans outstanding on the Advance Termination
                  Date by sixteen (16); and

         SECTION 2.03      AMENDMENT TO SECTION 2.4(a). SECTION 2.4(a) of the
Credit Agreement is hereby deleted and the following new SECTION 2.4(a) is
substituted in lieu thereof:

                  (a)      Interest Rate. Borrowers shall, jointly and
                  severally, pay to the Bank interest on the unpaid principal
                  amount outstanding hereunder, at a fluctuating rate per annum
                  equal to the Applicable Rate. The term "APPLICABLE RATE"
                  means: (i) with respect to each Base Rate Loan, the Base Rate;
                  (ii) with respect to each Libor Loan, the Adjusted Libor Rate
                  plus (A) prior to the Advance Termination Date, two and one
                  quarter percent (2.25%), and (B) on or after the Advance
                  Termination Date, two and one half percent (2.50%).

         SECTION 2.04      AMENDMENTS TO SECTION 8.1.

                  (a)      SECTION 8.1(j) of the Credit agreement is hereby
amended by deleting the word "and" at the end thereof.

                  (b)      SECTION 8.1(k) of the Credit Agreement is hereby
amended by deleting "." from the end thereof and substituting "; and" in lieu
thereof.

                  (c)      SECTION 8.1 of the Credit Agreement is hereby amended
by adding the following new SECTION 8.1(l) thereto:

                           (l)      Commercial Paper Debt.

         SECTION 2.05      AMENDMENT TO ARTICLE VIII. ARTICLE VIII of the Credit
Agreement is hereby amended by adding the following new Section thereto:

                           Section 8.12. Student Loan Servicing Rights. NLSI
                           shall not sell, transfer, or otherwise dispose of any
                           of its rights to service Student Loans pursuant to
                           the Servicing Contracts (as defined in the Security
                           Agreement) nor shall any other Subsidiary of NELNET
                           or NLSI begin servicing any Student Loans without the
                           prior written consent of Bank and delivery to Bank of
                           a pledge agreement, in form and substance
                           satisfactory to Bank, by the new servicer of such
                           Student Loans securing payment to Bank of the
                           Obligations.

                                                                 FIRST AMENDMENT

                                       3
<PAGE>

         SECTION 2.06      AMENDMENT TO SECTION 10.1. SECTION 10.1 of the Credit
Agreement is hereby amended by deleting SECTION 10.1(o) therefrom in its
entirety.

                                   ARTICLE III
                           CONDITIONS TO EFFECTIVENESS

         SECTION 3.01      CONDITIONS TO EFFECTIVENESS. This Amendment shall
become effective upon receipt by Bank of the following, each in form and
substance satisfactory to Bank and in such number of counterparts as may be
reasonably requested by Bank:

                  (a)      This Amendment duly executed by Borrowers, Bank, and
         each Guarantor (as defined in the Guaranty).

                  (b)      Borrower shall have paid to Bank a renewal and
         amendment fee equal to $30,000.

                  (c)      A certificate of incumbency for each Borrower
         certified by its Secretary or an Assistant Secretary certifying (i) the
         name of each of its officers who is authorized to sign this Amendment,
         and (ii) a true and correct copy of the Resolutions of the Board of
         Directors of each Borrower which authorize its execution and delivery
         of this Amendment, and the performance of the Loan Documents as amended
         hereby.

                  (d)      A Subsidiary Joinder Agreement executed by each
         Regular Subsidiary that is not a Guarantor (as defined in the Guaranty)
         under the Guaranty.

                                   ARTICLE IV
                        REPRESENTATIONS AND WARRANTIES

         In order to induce Bank to enter into this Amendment, Borrowers hereby
represent and warrant to Bank as follows:

         SECTION 4.01      CREDIT AGREEMENT. After giving effect to the
execution and delivery of this Amendment and the consummation of the
transactions contemplated hereby, and with this Amendment constituting one of
the Loan Documents, the representations and warranties set forth in Article VI
of the Credit Agreement are true and correct on the date hereof as though made
on and as of such date.

         SECTION 4.02      NO DEFAULT. After giving effect to the execution and
delivery of this Amendment and the consummation of the transactions contemplated
hereby, no Default or Event of Default has occurred and is continuing as of the
date hereof.

                                    ARTICLE V
                                  MISCELLANEOUS

         SECTION 5.01      AFFIRMATION OF LOAN DOCUMENTS. Borrowers hereby
acknowledge and agree that all of their obligations under the Credit Agreement,
as amended hereby, and the other Loan Documents, including but not limited to
the obligations of NLSI under the Security Agreement, shall remain in full force
and effect following the execution and delivery of this Amendment, and such
obligations are hereby affirmed, ratified, and confirmed by Borrowers.

         SECTION 5.02      COSTS AND EXPENSES. Borrowers agree to pay on demand
all costs and expenses incurred by Bank in connection with the preparation,
execution, delivery, filing, administration, and recording of this Amendment and
any other agreements delivered in connection with or pursuant to this

                                                                 FIRST AMENDMENT

                                       4
<PAGE>

Amendment, including, without limitation, the fees and out-of-pocket expenses
of Haynes and Boone, LLP, counsel to Bank.

         SECTION 5.03      SUCCESSORS AND ASSIGNS. This Amendment shall be
binding upon and inure to the benefit of the Borrowers and Bank and their
respective successors and assigns.

         SECTION 5.04      CAPTIONS. The captions in this Amendment have been
inserted for convenience only and shall be given no substantive meaning or
significance whatsoever in construing the terms and provisions of this
Amendment.

         SECTION 5.05      COUNTERPARTS. This Amendment may be executed in any
number of counterparts and by different parties hereto in separate counterparts,
each of which when so executed and delivered either in original, facsimile or
electronic form, shall be deemed to be an original but all of which taken
together shall constitute but one and the same instrument.

         SECTION 5.06      GOVERNING LAW. This Amendment shall be governed by,
and construed in accordance with, the laws of the State of Texas.

         SECTION 5.07      FINAL AGREEMENT OF THE PARTIES. THE CREDIT AGREEMENT
(INCLUDING THE EXHIBITS THERETO), AS AMENDED BY THIS AMENDMENT, THE NOTE, AND
THE OTHER LOAN DOCUMENTS REPRESENT THE FINAL AGREEMENT AMONG THE PARTIES AND MAY
NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS, OR SUBSEQUENT ORAL
AGREEMENTS OF THE PARTIES. THERE ARE NO UNWRITTEN ORAL AGREEMENTS AMONG THE
PARTIES.

  [Remainder of Page Intentionally Left Blank; Signatures Begin on Next Page]

                                                                 FIRST AMENDMENT

                                        5

<PAGE>

         IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
executed by their respective officers thereunto duly authorized as of the date
first above written.

                              BORROWERS

                              NELNET LOAN SERVICES, INC.
                              NELNET, INC.

                              BY: /s/ Terry J. Heimes
                                  ----------------------------------------------
                                  Name: Terry J. Heimes, Chief Financial Officer

                     SIGNATURE PAGE TO THE FIRST AMENDMENT

<PAGE>

                                  BANK OF AMERICA, N. A.,
                                  as Bank

                                  BY: /s/ Shelly K. Harper
                                      ------------------------------------------
                                      Shelly K. Harper, Principal

                     SIGNATURE PAGE TO THE FIRST AMENDMENT
<PAGE>

                              CONSENT OF GUARANTORS

To induce Bank to enter into this Amendment, the undersigned jointly and
severally (a) consent and agree to the execution and delivery of the Amendment,
(b) ratify and confirm that all guaranties, assurances, and liens granted,
conveyed, or assigned to Bank under the Loan Documents are not released,
diminished, impaired, reduced, or otherwise adversely affected by this Amendment
and continue to guarantee, assure, and secure the full payment and performance
of all present and future Obligations.

                                  GUARANTORS:

                                  NELNET LOAN SERVICES, INC.
                                  NELNET, INC.
                                  NELNET GUARANTEE SERVICES, INC.
                                  GUARANTEC, LLP
                                  NELNET MARKETING SOLUTIONS, INC.
                                  CLASSCREDIT, INC.
                                  INTUITION, INC.
                                  NHELP, INC.
                                  NATIONAL HIGHER EDUCATION
                                  LOAN PROGRAM, INC.
                                  EFS, INC.
                                  EFS FINANCE COMPANY
                                  EFS SERVICES INC.

                                  By: /s/ Terry J. Heimes
                                      ------------------------------------------
                                          Terry J. Heimes
                                      Name:-------------------------------------
                                           Authorized Officer of each Guarantor

                                GUARANTOR CONSENT

<PAGE>

                          SUBSIDIARY JOINDER AGREEMENT


         This SUBSIDIARY JOINDER AGREEMENT (the "AGREEMENT") dated as of
January 24, 2003 is executed by the undersigned (the "OBLIGATED PARTY") for the
benefit of BANK OF AMERICA, N.A., as agent for itself and the other Secured
Parties in connection with that certain Credit Agreement dated January 11, 2002,
among NELNET LOAN SERVICES, INC., NELNET, INC. (together the "BORROWERS") and
BANK OF AMERICA, N.A. (the "BANK") (as modified, the "CREDIT AGREEMENT", and
capitalized terms not otherwise defined herein being used herein as defined in
the Credit Agreement).

         The Obligated Party is a newly formed or newly acquired Subsidiary (but
not a Special Purpose Vehicle) and is required to execute this Agreement
pursuant to the Credit Agreement.

         NOW THEREFORE, in consideration of the premises and other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the Obligated Party hereby agrees as follows:

         1.       The Obligated Party hereby assumes all the obligations of a
"GUARANTOR" under the Guaranty and agrees that it is a "GUARANTOR" and is bound
as a "GUARANTOR" under the terms of the Guaranty as if it had been an original
signatory thereto. In accordance with the forgoing and for valuable
consideration, the receipt and adequacy of which are hereby acknowledged,
Obligated Party irrevocably and unconditionally guarantees to the Agent and the
Secured Parties the full and prompt payment and performance of the Guaranteed
Indebtedness (as defined in the Guaranty) upon the terms and conditions set
forth in the Guaranty.

         2.       This Agreement shall be deemed to be part of, and a
modification to, the Guaranty and shall be governed by all the terms and
provisions of the Guaranty, which terms are incorporated herein by reference,
are ratified and confirmed and shall continue in full force and effect as valid
and binding agreements of Obligated Party enforceable against Obligated Party.
The Obligated Party hereby waives notice of the Agent's or any Secured Party's
acceptance of this Agreement.

         IN WITNESS WHEREOF, the Obligated Party has executed this Agreement as
of the day and year first written above.

                                    Obligated Party:

                                    STUDENT PARTNER SERVICES, INC., a
                                    Nebraska corporation

                                    By: /s/ Terry J. Heimes
                                        ----------------------------------------
                                        Name: ----------------------------------
                                        Title:----------------------------------

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                          SUBSIDIARY JOINDER AGREEMENT

         This SUBSIDIARY JOINDER AGREEMENT (the "AGREEMENT") dated as of January
24, 2003 is executed by the undersigned (the "OBLIGATED PARTY") for the
benefit of BANK OF AMERICA, N.A., as agent for itself and the other Secured
Parties in connection with that certain Credit Agreement dated January 11, 2002,
among NELNET LOAN SERVICES, INC., NELNET, INC. (together the "BORROWERS") and
BANK OF AMERICA, N.A. (the "BANK") (as modified, the "CREDIT AGREEMENT", and
capitalized terms not otherwise defined herein being used herein as defined in
the Credit Agreement).

         The Obligated Party is a newly formed or newly acquired Subsidiary (but
not a Special Purpose Vehicle) and is required to execute this Agreement
pursuant to the Credit Agreement.

         NOW THEREFORE, in consideration of the premises and other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the Obligated Party hereby agrees as follows:

         1.       The Obligated Party hereby assumes all the obligations of a
"GUARANTOR" under the Guaranty and agrees that it is a "GUARANTOR" and is bound
as a "GUARANTOR" under the terms of the Guaranty as if it had been an original
signatory thereto. In accordance with the forgoing and for valuable
consideration, the receipt and adequacy of which are hereby acknowledged,
Obligated Party irrevocably and unconditionally guarantees to the Agent and the
Secured Parties the full and prompt payment and performance of the Guaranteed
Indebtedness (as defined in the Guaranty) upon the terms and conditions set
forth in the Guaranty.

         2.       This Agreement shall be deemed to be part of, and a
modification to, the Guaranty and shall be governed by all the terms and
provisions of the Guaranty, which terms are incorporated herein by reference,
are ratified and confirmed and shall continue in full force and effect as valid
and binding agreements of Obligated Party enforceable against Obligated Party.
The Obligated Party hereby waives notice of the Agent's or any Secured Party's
acceptance of this Agreement.

         IN WITNESS WHEREOF, the Obligated Party has executed this Agreement as
of the day and year first written above.

                                    Obligated Party:

                                    NELNET CANADA, INC., a Canadian
                                    corporation

                                    By: /s/ Terry J. Heimes
                                        ----------------------------------------
                                        Name: ----------------------------------
                                        Title:----------------------------------


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<PAGE>


                          SUBSIDIARY JOINDER AGREEMENT

         This SUBSIDIARY JOINDER AGREEMENT (the "AGREEMENT") dated as of January
24, 2003 is executed by the undersigned (the "OBLIGATED PARTY") for the benefit
of BANK OF AMERICA, N.A., as agent for itself and the other Secured Parties in
connection with that certain Credit Agreement dated January 11, 2002, among
NELNET LOAN SERVICES, INC., NELNET, INC. (together the "BORROWERS") and BANK OF
AMERICA, N.A. (the "BANK") (as modified, the "CREDIT AGREEMENT", and capitalized
terms not otherwise defined herein being used herein as defined in the Credit
Agreement).

         The Obligated Party is a newly formed or newly acquired Subsidiary (but
not a Special Purpose Vehicle) and is required to execute this Agreement
pursuant to the Credit Agreement.

         NOW THEREFORE, in consideration of the premises and other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the Obligated Party hereby agrees as follows:

         1.       The Obligated Party hereby assumes all the obligations of a
"GUARANTOR" under the Guaranty and agrees that it is a "GUARANTOR" and is bound
as a "GUARANTOR" under the terms of the Guaranty as if it had been an original
signatory thereto. In accordance with the forgoing and for valuable
consideration, the receipt and adequacy of which are hereby acknowledged,
Obligated Party irrevocably and unconditionally guarantees to the Agent and the
Secured Parties the full and prompt payment and performance of the Guaranteed
Indebtedness (as defined in the Guaranty) upon the terms and conditions set
forth in the Guaranty.

         2.       This Agreement shall be deemed to be part of, and a
modification to, the Guaranty and shall be governed by all the terms and
provisions of the Guaranty, which terms are incorporated herein by reference,
are ratified and confirmed and shall continue in full force and effect as valid
and binding agreements of Obligated Party enforceable against Obligated Party.
The Obligated Party hereby waives notice of the Agent's or any Secured Party's
acceptance of this Agreement.

         IN WITNESS WHEREOF, the Obligated Party has executed this Agreement as
of the day and year first written above.

                                           Obligated Party:

                                           IDAHO FINANCIAL ASSOCIATES, INC.,
                                           an Idaho corporation

                                           By: /s/ Terry J. Heimes
                                               ---------------------------------
                                               Name:  --------------------------
                                               Title: --------------------------

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<PAGE>

                          SUBSIDIARY JOINDER AGREEMENT

         This SUBSIDIARY JOINDER AGREEMENT (the "AGREEMENT") dated as of January
24, 2003 is executed by the undersigned (the "OBLIGATED PARTY") for the benefit
of BANK OF AMERICA, N.A., as agent for itself and the other Secured Parties in
connection with that certain Credit Agreement dated January 11, 2002, among
NELNET LOAN SERVICES, INC., NELNET, INC. (together the "BORROWERS") and BANK OF
AMERICA, N.A. (the "BANK") (as modified, the "CREDIT AGREEMENT", and capitalized
terms not otherwise defined herein being used herein as defined in the Credit
Agreement).

         The Obligated Party is a newly formed or newly acquired Subsidiary (but
not a Special Purpose Vehicle) and is required to execute this Agreement
pursuant to the Credit Agreement.

         NOW THEREFORE, in consideration of the premises and other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the Obligated Party hereby agrees as follows:

         1.       The Obligated Party hereby assumes all the obligations of a
"GUARANTOR" under the Guaranty and agrees that it is a "GUARANTOR" and is bound
as a "GUARANTOR" under the terms of the Guaranty as if it had been an original
signatory thereto. In accordance with the forgoing and for valuable
consideration, the receipt and adequacy of which are hereby acknowledged,
Obligated Party irrevocably and unconditionally guarantees to the Agent and the
Secured Parties the full and prompt payment and performance of the Guaranteed
Indebtedness (as defined in the Guaranty) upon the terms and conditions set
forth in the Guaranty.

         2.       This Agreement shall be deemed to be part of, and a
modification to, the Guaranty and shall be governed by all the terms and
provisions of the Guaranty, which terms are incorporated herein by reference,
are ratified and confirmed and shall continue in full force and effect as valid
and binding agreements of Obligated Party enforceable against Obligated Party.
The Obligated Party hereby waives notice of the Agent's or any Secured Party's
acceptance of this Agreement.

         IN WITNESS WHEREOF, the Obligated Party has executed this Agreement as
of the day and year first written above.

                                    Obligated Party:

                                    CHARTER SERVICES, INC., a New York
                                    corporation

                                    By: /s/ Terry J. Heimes
                                        ----------------------------------------
                                        Name: ----------------------------------
                                        Title:----------------------------------

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