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                                                                   EXHIBIT 10.23


               THIRD AMENDMENT TO AMENDED AND RESTATED WAREHOUSING
                         CREDIT AND SECURITY AGREEMENT


      This Third Amendment to the Amended and Restated Warehousing Credit and
Security Agreement (this "Amendment"), is entered into effective as of the 30th
day of April, 2001 by and among MORTGAGE PORTFOLIO SERVICES, INC., a Delaware
corporation ("Company"), NAB ASSET CORPORATION ("Guarantor"), WASHINGTON MUTUAL
BANK, FA, a federal association, successor by merger to BANK UNITED, in its
capacity as one of the Lenders and Administrative Agent and Collateral Agent for
the Lenders ("Agent"), the lenders party to the Warehouse Agreement, as defined
below ("Lenders"), CENTEX FINANCIAL SERVICES, INC., a Nevada corporation
("Centex"), and CENTEX CORPORATION, a Nevada corporation.

      Section 1. Recitals. Company, Agent, and Lenders have entered into that
certain Amended and Restated Warehousing Credit and Security Agreement dated
August 28, 2000 (as amended on October 15, 2000 and November 13, 2000, the
"Warehouse Agreement") for the purposes and consideration therein expressed,
pursuant to which Lenders have agreed to make loans to Company as therein
provided. Company, Guarantor, Centex, Centex Corporation, Agent, and Lenders
desire to amend the Warehouse Agreement to extend the Termination Date of the
Commitment and make such other modifications as more particularly set forth
herein. Therefore, Company, Guarantor, Centex, Centex Corporation, Agent, and
Lenders hereby agree as follows, intending to be legally bound:

      Section 2. Definitions and References. Unless the context otherwise
requires or unless otherwise expressly defined herein, the terms in the
Warehouse Agreement shall have the same meanings whenever used in this
Amendment.

      Section 3. Amendments. The Warehouse Agreement is hereby amended, as
follows:

            (a) The following definitions are hereby added to Section 1.1 of the
      Warehouse Agreement:

            "'Centex' shall mean Centex Financial Services, Inc., a Nevada
      corporation."

            "'Defective Collateral' means any Collateral that is not or ceases
      to be an Eligible Mortgage Loan, an Eligible Construction Mortgage Loan,
      an Eligible Past Due Loan, an Eligible Delinquent Loan, an Eligible
      Foreclosure Mortgage Loan, an Eligible Repurchased Mortgage Loan, or an
      Eligible REO."

            "'Stock Purchase Agreement' means the Stock Purchase Agreement dated
      as of March 16, 2001 between Centex, Stanwich Financial Services Corp.,
      and NAB Asset Corporation, as amended."

      (b) The following definition in Section 1.1 of the Warehouse Agreement is
hereby amended as follows:

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            "'Termination Date' shall mean the earlier to occur of (i) August
      31, 2001, or (ii) the date which is two (2) Business Days following the
      Administrative Agent's receipt of Notice from Centex that the Stock
      Purchase Agreement has terminated or will terminate or (iii) such earlier
      date upon which Lenders' obligation to fund shall be terminated pursuant
      to the terms of this Agreement."

      (c) The following Section 2.5(a) of the Warehouse Agreement is hereby
restated as follows:

            "The outstanding unpaid principal amount of all Advances shall be
      payable in full on the date that is sixty (60) days following the
      Termination Date."

      (d) The following section is hereby added to the end of Article 6
Affirmative Covenants. of the Warehouse Agreement for all purposes:

            "6.15 Mandatory Payment by Centex. If the Company fails to pay to
      the Administrative Agent at any time and from time to time (i) all
      outstanding Advances against any Defective Collateral plus any accrued and
      unpaid interest thereon in accordance with this Agreement, (ii) the entire
      outstanding principal amount of all Advances plus all accrued and unpaid
      interest thereon in full on the date that is sixty (60) days following the
      Termination Date and/or (iii) all accrued and unpaid fees due and payable
      to the Administrative Agent or the Lenders pursuant to Section 2.8 of this
      Agreement (all of the unpaid amounts described in (i), (ii), and (iii) are
      hereinafter collectively called the "Past Due Amounts"), Centex shall,
      absolutely and unconditionally, pay to Administrative Agent, for the
      benefit of the Lenders, all such Past Due Amounts in immediately available
      funds within five (5) Business Days after receiving Notice (which shall be
      sent by facsimile and confirmed by mail) from Administrative Agent of such
      failure; provided, however, that Centex shall not be liable for the
      repayment of any Advances made by Administrative Agent or the Lenders to
      Company after the Termination Date and all accrued and unpaid interest on
      such Advances (without implying any obligation to make Advances after the
      Termination Date) or any fees payable pursuant to Section 2.8 of this
      Agreement accruing after the Termination Date. Administrative Agent shall
      provide in its Notice to Centex a description in reasonable detail of the
      Past Due Amounts together with a list of all Pledged Mortgages
      specifically relating to such Past Due Amounts (including Pledged
      Mortgages in respect of which Wet Advances have been made) and the Past
      Due Amount owed against each Pledged Mortgage; such list shall be
      substantially in the form of EXHIBIT "T" hereto. With respect to Past Due
      Amounts relating to Defective Collateral, Administrative Agent's Notice
      shall describe the defects that have resulted in such Collateral becoming
      Defective Collateral."

      (e) Section 7.5 of the Warehouse Agreement is hereby restated as follows:

            "7.5. Minimum Consolidated Tangible Net Worth Ratio. Permit the
      ratio of Debt to Company's Consolidated Tangible Net Worth to exceed 15:1,
      computed as of the end of each calendar month. For the purposes of this
      calculation and the calculation required in Section 7.6 below, Debt and
      Consolidated liabilities of the Company shall not include the Subordinated
      Debt of the Company."

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      (f) The following event is hereby added to the end of Section 8.1 Events
of Default. of the Warehouse Agreement for all purposes:

            "(q) Centex fails to pay and perform its obligations pursuant to
      Section 6.15 of this Agreement by the deadline specified in that Section."

      (g) Article 9 of the Warehouse Agreement is hereby restated as follows:

            "9. Notices. Any notice, request or other communication required or
      permitted to be given under or in connection with this Agreement, the
      Notes or the other Loan Documents ("Notices") (except as may otherwise be
      expressly required therein) shall be in writing and shall be mailed by
      first class or express mail, postage prepaid, or sent by facsimile,
      confirmed by mailing (by first class or express mail, postage prepaid)
      written confirmation at substantially the same time as such facsimile, or
      personally delivered to an officer of the receiving party. All such
      communications shall be mailed, sent, delivered, or faxed to the parties
      hereto at their respective addresses or facsimile numbers as follows:

      If to the Company:            Mortgage Portfolio Services, Inc.
                                    5520 LBJ Freeway
                                    Suite 200
                                    Dallas, Texas 75240
                                    Attn:  James E. Hinton
                                    Facsimile:  (214) 821-7352
                                    Telephone:  (972) 341-8510

      With copies to Centex and Centex Corporation by facsimile (confirmed by
      mail) at their respective addresses specified below.

      If to the Guarantor:          NAB Asset Corporation
                                    4144 N. Central Expressway, Suite 900
                                    Dallas, Texas 75204
                                    Attn: Alan Ferree
                                    Facsimile:  (214) 821-3689
                                    Telephone:  (214) 860-1882

      If to Centex:                 Centex Financial Services, Inc.
                                    Attn:  Jim Hillsman
                                    2828 N. Harwood
                                    Dallas, Texas 75201-1516
                                    Facsimile: (214) 758-7814
                                    Telephone: (214) 981-7771

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      If to Centex Corporation:     Centex Corporation
                                    Attn:  Larry Angelilli
                                    2728 N. Harwood
                                    Dallas, Texas 75201-1516
                                    Facsimile: (214) 981-6858
                                    Telephone: (214) 981-6505

      If to Washington Mutual as Administrative Agent, Collateral Agent or a
      Lender:

                                    Washington Mutual Bank, FA
                                    Attn: Frank Hattemer
                                    3200 Southwest Freeway, Suite 2702
                                    Houston, Texas 77027
                                    Facsimile: (713) 543-6022
                                    Telephone:  (713) 543-6486

      If to Residential Funding Corporation:

                                    Residential Funding Corporation
                                    Attn:  Jim Clapp
                                    4800 Montgomery Lane, Suite 300
                                    Bethesda, Maryland 20814
                                    Facsimile: (301 215-6239
                                    Telephone: (301) 215-6288

      or at such other addresses or to such individual's or department's
      attention or at such other facsimile numbers as any party may have
      furnished the other party in writing. Any Notice addressed and mailed
      shall be deemed to be given when so mailed, except that Advance Requests,
      and communications related thereto shall not be effective until actually
      received by Administrative Agent or Company, as the case may be. Any
      Notice sent by facsimile shall be deemed to be given when receipt of such
      facsimile is acknowledged. Any Notice delivered in person shall be deemed
      to be given when receipted for by, or actually received by, an authorized
      officer of the receiving party."

      (h) EXHIBIT "T" to this Amendment is hereby added as EXHIBIT "T" to the
Warehouse Agreement for all purposes.

      Section 4. Representations and Other Agreements. (a) Company represents
and warrants that all of the representations and warranties contained in the
Warehouse Agreement and all instruments and documents executed pursuant thereto
or contemplated thereby are true and correct in all material respects on and as
of this date. Agent represents and warrants to Centex that it has provided to
Centex accurate and complete copies of the Warehouse Agreement and the Notes in
effect as of the date hereof.

      (b) Notwithstanding anything contained in the Warehouse Agreement, as
amended hereby, or in any other Loan Document to the contrary, Company agrees
that it shall not request or be entitled to receive any Advances on or after the
Termination Date.

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      (c) The maturity date of each Lender's Note is hereby renewed and extended
to sixty (60) days following the Termination Date.

      (d) The Loan Documents, as amended hereby, may not be amended or modified
by the Company, the Guarantor, the Agent, and the Lenders without the prior
written consent of Centex and Centex Corporation.

      (e) If at any time and from time to time Centex or Centex Corporation pays
to the Agent all Past Due Amounts specified in any Notice given by Agent in
accordance with Section 6.15 of the Warehouse Agreement, as amended hereby,
Company hereby directs the Agent to assign, release, and deliver, and Agent
hereby agrees to assign, release, and deliver, free and clear of the Agent's and
Lenders' Liens, to Centex, within two (2) Business Days of Agent's receipt of
Centex's or Centex Corporation's payment of all such Past Due Amounts in
immediately available funds, (i) all original Mortgage Notes (duly endorsed in
blank) held by Agent evidencing the Pledged Mortgages specifically relating to
such Past Due Amounts ("Past Due Mortgages"), and (ii) any and all other
Collateral Documents specifically relating to such Past Due Mortgages, if any,
held by the Agent under the Loan Documents. If the Agent thereafter receives any
Mortgage Notes or other Collateral Documents specifically relating to such Past
Due Mortgages (including Past Due Mortgages in respect of which Wet Advances
were made or sent to Investors for purchase) or any cash or non-cash proceeds
relating to any of the Past Due Mortgages, or any overpayments of amounts
payable by Centex under Section 6.15 of the Warehouse Agreement, Company hereby
directs Agent to assign, release, and deliver, and Agent hereby agrees to
assign, release and deliver, free and clear of Agent's and Lenders' Liens, to
Centex, promptly but in any event within two (2) Business Days of Agent's
receipt, all such Mortgage Notes, Collateral Documents, proceeds and
overpayments.

      Section 5. Severability. In the event any one or more provisions contained
in the Warehouse Agreement or this Amendment should be held to be invalid,
illegal or unenforceable in any respect, the validity, enforceability and
legality of the remaining provisions contained herein and therein shall not be
affected in any way or impaired thereby and shall be enforceable in accordance
with their respective terms.

      Section 6. Expenses. Company agrees to pay all out-of-pocket costs and
expenses (including reasonable attorney's fees and expenses) of the Agent and
the Lenders in connection with the preparation, operation, administration and
enforcement of this Amendment.

      Section 7. Ratification of Agreements. (a) Except as amended hereby,
Company ratifies and confirms that the Warehouse Agreement and all other Loan
Documents are and remain in full force and effect in accordance with their
respective terms and that all Collateral is unimpaired by this Amendment and
secures the payment and performance of all indebtedness and obligations of
Company under the Notes, the Warehouse Agreement, and all other Loan Documents,
as modified hereby.

      (b) Each of the undersigned officers of Company, Guarantor, Centex, and
Centex Corporation executing this Amendment represents and warrants that he has
full power and authority to execute and deliver this Amendment on behalf of the
party for whom he is executing this Amendment, that such execution and delivery
has been duly authorized by all necessary corporate action of such party, and
with respect to the Company and Guarantor, each of its respective officers
represents and warrants that the resolutions and affidavits previously delivered
to Agent, in connection

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with the execution and delivery of the Warehouse Agreement, are and remain in
full force and effect and have not been altered, amended or repealed in anywise.

      (c) Any reference to the Warehouse Agreement in any Loan Document shall be
deemed to be references to the Warehouse Agreement as amended hereby.

      (d) Except as amended hereby, each of the Agent and the Lenders ratifies
and confirms that the Warehouse Agreement and all other Loan Documents are and
remain in full force and effect in accordance with their respective terms.

      (e) Each of the undersigned officers of the Agent and the Lenders
represents and warrants that he has full power and authority to execute and
deliver this Amendment on behalf of the party for whom he is executing this
Amendment and that such execution and delivery has been duly authorized.

      Section 8. No Waiver. Company agrees that no Event of Default and no
Default has been waived or remedied by the execution of this Amendment by Agent
and Lenders, and any such Default or Event of Default heretofore arising and
currently continuing shall continue after the execution and delivery hereof.
Agent and Lenders represent and warrant to Centex that they are not aware of any
Default or Event of Default that is existing as of the date hereof.

      Section 9. Governing Law. This Amendment shall be governed by and
construed in accordance with the laws of the State of Texas and, to the extent
applicable, by federal law.

      Section 10. Counterparts and Gender. This Amendment may be executed in any
number of counterparts and all of such counterparts taken together shall be
deemed to constitute one and the same instrument. Each gender used herein shall
include and apply to all genders, including the neuter.

      Section 11. Joinder of Centex and Centex Corporation. (a) Centex is joined
herein to evidence its agreement to the terms, conditions and agreements
contained in this Amendment and to observe, pay and perform the obligations set
forth in Section 6.15 of the Warehouse Agreement, as amended hereby. Centex
hereby acknowledges that but for such agreements, Agent and Lenders would not
enter into this Amendment.

      (b) Centex Corporation hereby, unconditionally and absolutely, guarantees
to the Agent, on behalf of the Lenders, the prompt and punctual payment and
performance when due (whether at its maturity, by lapse of time, by
acceleration, or otherwise) of all indebtedness, liabilities, and obligations
("Guaranteed Obligations") of Centex under this Amendment and Section 6.15 of
the Warehouse Agreement, as amended hereby. The foregoing guaranty is an
absolute guaranty of payment and not a guaranty of collection. Centex
Corporation agrees to pay Agent the Guaranteed Obligations upon demand and all
of its out-of-pocket collection costs relating to the enforcement of Centex
Corporation's obligations hereunder, including any additional amount for
reasonable attorney's fees, if the Guaranteed Obligations are not paid by Centex
Corporation upon demand or if the obligations of Centex Corporation hereunder
are enforced by suit, or through probate or bankruptcy court or through any
judicial proceedings whatsoever. Centex Corporation hereby expressly waives each
and every right to which it may be entitled by virtue of the suretyship laws of
the State of Texas including, without limitation, any rights it may have
pursuant to Rule 31, Texas Rules of Civil Procedure, V.T.C.A. Civil Practice and
Remedies Code Section 17.00 and Chapter 34 of the Texas Business and Commerce
Code.

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Centex Corporation acknowledges that but for its guaranty the Agent and the
Lenders would not enter into this Amendment.

      Section 12. Further Assurances. Company agrees to do such further acts and
things and execute and deliver to Centex such additional assignments, powers and
instruments as are reasonably required by Centex to carry into effect the
release and delivery to Centex of the Mortgage Loans and other Collateral
required to be released and delivered to it under Section 4(e) hereof.

      SECTION 13. NO ORAL AGREEMENTS. THIS AMENDMENT AND THE OTHER LOAN
DOCUMENTS REPRESENT THE FINAL AGREEMENT BETWEEN THE PARTIES AND MAY NOT BE
CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS OR ORAL AGREEMENTS OF THE
PARTIES.

      THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN THE PARTIES.

                            [Signature Pages Follow]

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      EXECUTED this 30th day of April, 2001.

                                        COMPANY:

                                        MORTGAGE PORTFOLIO SERVICES, INC.,
                                        a Delaware corporation


                                        By: s/s James E. Hinton
                                            ------------------------------------
                                        James E. Hinton, President

                                        NOTICE ADDRESS:

                                        Mortgage Portfolio Services, Inc.
                                        4144 North Central Expressway
                                        Suite 800
                                        Dallas, Texas 75204
                                        Attn:  James E. Hinton
                                        Facsimile: (214) 821-7352
                                        Telephone: (972) 341-8510

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                                        GUARANTOR:

                                        NAB ASSET CORPORATION,
                                        a Texas corporation


                                        By: s/s Alan Ferree
                                            ------------------------------------
                                        Name: Alan Ferree
                                        Title: SVP

                                        NOTICE ADDRESS:

                                        NAB Asset Corporation
                                        4144 N. Central Expressway, Suite 900
                                        Dallas, Texas 75204
                                        Attn: Alan Ferree
                                        Facsimile: (214) 821-3689
                                        Telephone: (214) 860-1882

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                               WASHINGTON MUTUAL BANK, F.A., successor by merger
                               to BANK UNITED, as Administrative Agent and a
                               Lender


                               By: s/s Patrick C. Freeman
                                   ---------------------------------------------
                                      Patrick C. Freeman, AVP
                                      Mortgage Banker Finance

                               NOTICE ADDRESS:

                               Washington Mutual Bank, F.A.,
                               successor by merger to Bank United
                               Attn: Frank Hattemer, Director
                               Mortgage Banker Finance
                               3200 Southwest Freeway, Suite 2702
                               Houston, Texas 77027
                               Facsimile: (713) 543-4292
                               Telephone: (713) 543-6486

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                                        RESIDENTIAL FUNDING CORPORATION,
                                        a Delaware corporation, as a  Lender


                                        By: s/s Jim Clapp
                                            ------------------------------------
                                        Name: Jim Clapp
                                        Title: Director


                                        NOTICE ADDRESS:
                                        Residential Funding Corporation
                                        Attn:  Thomas M. Clement
                                        4800 Montgomery Lane, Suite 300
                                        Bethesda, Maryland 20814
                                        Facsimile:  (301) 215-6288
                                        Telephone: (301) 215-6239

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                                        CENTEX FINANCIAL SERVICES,  INC.,
                                        a Nevada corporation


                                        By: s/s Larry Brown
                                            ------------------------------------
                                        Name: Larry Brown
                                        Title: Assistant Treasurer

                                        NOTICE ADDRESS:

                                        Attn:  Jim Hillsman
                                        2828 N. Harwood
                                        Dallas, Texas 75201-1516
                                        Facsimile: (214) 758-7814
                                        Telephone: (214) 981-7771

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                                        CENTEX CORPORATION,
                                        a Nevada corporation


                                        By: s/s Vicki A. Roberts
                                            ------------------------------------
                                        Name: Vicki A. Roberts
                                        Title: Vice President and Treasurer

                                        NOTICE ADDRESS:

                                        Attn:  Larry Angelilli
                                        2728 N. Harwood
                                        Dallas, Texas 75201-1516
                                        Facsimile: (214) 981-6858
                                        Telephone: (214) 981-6505

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