<PAGE>   1
                                                                    EXHIBIT 4.13

                               THIRD AMENDMENT TO
                                CREDIT AGREEMENT

     This Third Amendment to Credit Agreement (this "Third Amendment"), dated as
of July 9, 1997, is entered into by and among PULTE CORPORATION (the
"Borrower"), the lenders identified as such on the signature pages attached
hereto (the "Lenders"), the guarantors identified as such on the signature
pages attached hereto (the "Guarantors"), NATIONSBANK, N.A. f/k/a NationsBank,
N.A. (Carolinas) as agent for the Lenders (in such capacity, the "Agent") and
Comerica Bank and The First National Bank of Chicago as Co-Agents (the
"Co-Agents"). All capitalized terms used herein and not otherwise defined shall
have the meanings ascribed to such terms in the Credit Agreement (as defined
below).

                                    RECITALS

     A.   The Borrower, the Lenders, the Agent and the Co-Agents entered into
that certain Credit Agreement dated as of January 5, 1995 (as amended by that
certain First Amendment to Credit Agreement dated as of January 4, 1996 and that
certain Second Amendment to Credit Agreement dated as of December 31, 1996, the
"Credit Agreement").

     B.   The Guarantors (other than Pulte Lifestyle Communities, Inc.)
guaranteed all of the Borrower Obligations pursuant to those certain Guaranty
Agreements dated as of January 5, 1995, and Pulte Lifestyle Communities, Inc.
guaranteed all of the Borrower Obligations pursuant to that certain Guaranty
Agreement dated as of May 10, 1995 (as modified or reaffirmed from time to time,
collectively, the "Guaranty Agreements").

     C.   The Borrower has requested that the Credit Agreement be amended to
provide for Quoted Rate Swing Line Loans.

     D.   The Lenders have agreed to such modification pursuant to the terms set
forth below.

                                    AGREEMENT

     NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto agree as
follows:

1.   Definitions

          (a)  The following definitions are hereby added to Section 1.01 of the
     Credit Agreement, in the correct alphabetical order, to read as follows:

          "Quoted Rate" has the meaning set forth in Section 2.01A(c)(ii).

<PAGE>   2
          "Quoted Rate Swing Line Loan" means a Swing Line Loan accruing
     interest at a Quoted Rate.

          (b)  The definition of "Base Rate Loans" in Section 1.01 of the
     Credit Agreement is amended in its entirety to read as follows:

          "Base Rate Loans" means the Revolving Loans and the Swing Line Loans
     accruing interest at the Base Rate.

          (c) The first sentence of the definition of "Interest Payment Date" in
     Section 1.01 of the Credit Agreement is amended in its entirety to read as
     follows:

          "Interest Payment Date" means (a) as to Base Rate Loans, the last day
     of each month, (b) as to Quoted Rate Swing Line Loans, the last day of the
     Interest Period for each Quoted Rate Swing Line Loan, (c) as to CD Rate
     Loans and Eurodollar Loans, the last day of each applicable Interest
     Period; provided that if the Interest Period for a Eurodollar Loan is
     greater than 3 months or the Interest Period for a CD Rate Loan is greater
     than 90 days, then the Interest Payment Date shall be the last day of each
     fiscal quarter of the Borrower and the last day of the applicable Interest
     Period and (d) as to Competitive Bid Loans, the last day of the Interest
     Period for each Competitive Bid Loan; provided that if the Interest Period
     on a Competitive Bid Loan is greater than 90 days then the Interest Payment
     Date shall be the last day of each fiscal quarter of the Borrower and the
     last day of the applicable Interest Period.

          (d)  The definition of "Interest Period" is amended by deleting the
     word "and" directly before subsection (c), by inserting a comma after the
     word "borrowing" directly before subsection (c) and by inserting the
     following subsection directly before the semicolon:

          and (d) with respect to Quoted Rate Swing Line Loans a period
     beginning on the date of advance and ending on the date specified in the
     respective Swing Line Loan Request, which shall not be more than 7 days in
     duration

2.   Amendment to Section 2.01A(c)(ii). Section 2.01A(c)(ii) of the Credit
     Agreement is amended in its entirety to read as follows:

              (ii) Swing Line Borrowings. By no later than 2:00 p.m. on the date
          of the requested borrowing of Swing Line Loans, the Borrower shall
          submit a Swing Line Loan Request to NationsBank setting forth (A) the
          amount of the requested Swing Line Loan (which shall not be less than
          $500,000 and in integral multiples of $500,000 in excess thereof), (B)
          the date of the requested Swing Line Loan and (C) whether such Swing
          Line Loan is to be a Base Rate Loan or a Quoted Rate Swing


                                        2
<PAGE>   3
          Line Loan and if it is a Quoted Rate Swing Line Loan, the
          applicable Interest Period and complying in all respects with Section
          5. If the Borrower has requested a Quoted Rate Swing Line Loan,
          NationsBank shall provide to the Borrower, no later than 2:30 p.m. on
          the date of the request, the rate at which NationsBank would be
          willing to provide such Swing Line Loan (the "Quoted Rate"). The
          Borrower shall notify NationsBank by 3:00 p.m. on such date whether it
          wishes to accept the Quoted Rate. Failure of the Borrower to timely
          accept the Quoted Rate shall make the Quoted Rate and the
          corresponding Swing Line Loan Request void.

3.   Amendment to Section 2.01A(c)(iii). The first three sentences and the last
     two sentences of Section 2.01A(c)(iii) of the Credit Agreement are amended
     in their entirety to read as follows:

               (iii) Additional Swing Line Loan Provisions. The Borrower agrees
          to repay all Swing Line Loans that are Base Rate Loans within one
          Business Day of demand therefor by NationsBank and all Swing Line
          Loans that are Quoted Rate Swing Line Loans at the end of the
          applicable Interest Period. Each repayment of a Swing Line Loan may be
          accomplished by requesting Revolving-A Loans in accordance with
          Section 2.02. In the event that the Borrower shall fail to repay any
          Swing Line Loan within three Business Days after demand therefor by
          NationsBank or the termination of the applicable Interest Period, and
          in any event upon (1) a request by NationsBank, (2) the occurrence of
          an Event of Default described in Section 9.01(f) or (3) the
          acceleration of any Loan or termination of any Commitment pursuant to
          Section 9.01, each other Lender shall irrevocably and unconditionally
          purchase from NationsBank, without recourse or warranty, an undivided
          interest and participation in such Swing Line Loan in an amount equal
          to such other Lender's Commitment Percentage thereof, by directly
          purchasing a participation in such Swing Line Loan in such amount
          (regardless of whether the conditions precedent thereto set forth in
          Section 5.02 hereof are then satisfied, whether or not the Borrower
          has made an Advance Request and whether or not the Revolving-A Loan
          Commitments are then in effect, any Event of Default exists or all the
          Loans have been accelerated) and paying the proceeds thereof to
          NationsBank at the address provided in Section 11.01, or at such other
          address as NationsBank may designate, in Dollars and in immediately
          available funds; provided that a Lender is not required to purchase a
          participation in a Swing Line Loan that was made by NationsBank during
          the existence of a Default or an Event of Default that was known to
          exist by NationsBank when it made such Swing Line Loan.




          Upon the purchase of a participation in respect of such Swing Line
          Loan by a Lender pursuant to this Section 2.01A(c), the amount so
          funded by the purchasing


                                       3
<PAGE>   4
          Lender shall become a Revolving-A Loan accruing interest at the Base
          Rate and shall no longer be a Swing Line Loan. On the date that the
          Lenders are required to purchase participations in Swing Line Loans
          under this Section 2.01A(c), NationsBank's pro rata share of such
          Swing Line Loans shall no longer be a Swing Line Loan hereunder but
          shall be a Revolving-A Loan accruing interest at the Base Rate.

4.   Amendment to Section 3.01(a)(ix). Section 3.01(a)(ix) of the Credit
     Agreement is amended in its entirety to read as follows:

                    (ix) All Swing Line Loans shall accrue interest at the Base
               Rate or if such Swing Line Loan is a Quoted Rate Swing Line Loan,
               then such Swing Line Loan shall accrue interest at the Quoted
               Rate applicable thereto.

5.   Amendment to Section 3.02(a). Section 3.02(a) of the Credit Agreement is
     amended in its entirety to read as follows:

               (a) Voluntary Prepayments. The Borrower shall have the right to
          prepay Loans in whole or in part from time to time without premium or
          penalty; provided, however, that (i) Eurodollar Loans and CD Rate
          Loans may only be prepaid on three Business Day' prior written notice
          to the Agent and any prepayment of Eurodollar Loans or CD Rate Loans
          will be subject to Section 4.01(d); (ii) each such partial prepayment
          of Loans shall be in the minimum principal amount of $1,000,000; and
          (iii) Competitive Bid Loans and Quoted Rate Swing Line Loans may not
          be prepaid unless a breakage fee equal to the amount of actual damages
          suffered by the Lender whose Competitive Bid Loan or Quoted Rate Swing
          Line Loan is prepaid is paid to such Lender; provided that such Lender
          shall provide the Borrower with the calculation of such damages.
          Amounts prepaid hereunder shall be applied as the Borrower may elect;
          provided, that if the Borrower fails to specify a voluntary prepayment
          then such prepayment shall be applied first to Revolving Loans that
          are Base Rate Loans, then to CD Rate Loans in direct order of Interest
          Period maturities, then to Eurodollar Loans in direct order of
          Interest Period maturities, then to Swing Line Loans (first to Swing
          Line Loans that are Base Rate Loans and then to Quoted Rate Swing Line
          Loans in direct order of Interest Period maturities) and then to
          Competitive Bid Loans pro rata among all Lenders holding same.

  6.      Amendment to Section 3.02(b). The last sentence of Section 3.02(b) of
          the Credit Agreement is amended in its entirety to read as follows:

               (b) Mandatory Prepayments. Any payments made under this Section
          3.02(b) shall be applied first to Revolving Loans that are Base Rate
          Loans, then to CD Rate Loans in direct order of Interest Period
          maturities, then to Eurodollar Loans in direct order

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<PAGE>   5
of Interest Period maturities, then to Swing Line Loans (first to Swing Line
Loans that are Base Rate Loans and then to Quoted Rate Swing Line Loans in
direct order of Interest Period maturities) and then to Competitive Bid Loans
pro rata among all Lenders holding same.

7.   Exhibit 2.01A(c). Exhibit 2.01A(c).to the Credit Agreement is deleted in
     its entirety and replaced by the new Exhibit 2.01A(c) attached hereto as
     Exhibit A.

8.   Representations and Warranties. The Borrower hereby represents and warrants
     to the Lenders, the Agent and the Co-Agents that, as of the date hereof,
     (a) the representations and warranties set forth in Sections 6.01, 6.02,
     6.03, 6.04, 6.05, 6.14, 6.16 and 6.17 are true and correct (other than with
     respect to PFCI), (b) since the audited financial statements of the
     Consolidated Pulte Group dated as of December 31, 1996 which has been
     previously delivered to the Lenders, there have occurred no changes or
     circumstances which have had or are likely to have a material adverse
     effect on the financial condition of the Consolidated Pulte Group taken as
     a whole, (c) except as previously disclosed in its annual and quarterly
     filings with the Securities and Exchange Commission (none of which
     disclosed matters the Borrower deems to be material), there are no actions,
     suits or legal, equitable, arbitration or administrative proceedings
     pending or, to the knowledge of the Borrower, threatened against any member
     of the Consolidated Pulte Group which, if adversely determined, would
     likely have a material adverse effect on the financial or business
     condition of the Consolidated Pulte Group taken as a whole and (d) no
     Default or Event of Default exists and is continuing.

9.   Conditions Precedent. The effectiveness of this Third Amendment is subject
     to the receipt by the Agent of copies of this Third Amendment duly executed
     by the Borrower, the Guarantors and each of the Lenders.

10.  Acknowledgment of Guarantors. The Guarantors acknowledge and consent to
     all of the terms and conditions of this Third Amendment and agree that this
     Third Amendment and all documents executed in connection herewith do not
     operate to reduce or discharge the Guarantors' obligations under the
     Guaranty Agreements or the other Loan Documents.

11.  No Other Changes. Except as expressly modified and amended in this Third
     Amendment, all of the terms, provisions and conditions of the Loan
     Documents shall remain unchanged.

12.  Counterparts. This Third Amendment may be executed in any number of
     counterparts and by the parties hereto in separate counterparts, each of
     which when so executed and delivered shall be deemed to be an original and
     all of which taken together shall constitute one and the same instrument.


                                        5


<PAGE>   6





13.  ENTIRETY. THIS THIRD AMENDMENT AND THE OTHER LOAN DOCUMENTS EMBODY THE
     ENTIRE AGREEMENT BETWEEN THE PARTIES AND SUPERSEDE ALL PRIOR AGREEMENT'S
     AND UNDERSTANDINGS, ORAL OR WRITTEN, IF ANY, RELATING TO THE SUBJECT MATTER
     HEREOF.

14.  GOVERNING LAW. THIS THIRD AMENDMENT AND THE RIGHTS AND OBLIGATIONS OF THE
     PARTIES HEREUNDER SHALL BE GOVERNED BY AND CONSTRUED AND INTERPRETED IN
     ACCORDANCE WITH THE LAWS OF THE STATE OF NORTH CAROLINA.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK)




                                        6




<PAGE>   7





This Third Amendment is executed as of the day and year first written above.

                                   BORROWER

                                   PULTE CORPORATION

                                   By:  /s/    James A. Weissenborn
                                       ---------------------------------
                                   Name:       James A. Weissenborn
                                       ---------------------------------
                                   Title:      Treasurer/Vice President
                                       ---------------------------------



                                   GUARANTORS

                                   BUILDER'S SUPPLY & LUMBER CO., INC.

                                   By:  /s/    Calvin R. Boyd
                                      ---------------------------------
                                   Name:       Calvin R. Boyd
                                      ---------------------------------
                                   Title:      Assistant Secretary
                                      ---------------------------------

                                   FAIRMONT BUILDING CORPORATION

                                   By:  /s/    Calvin R. Boyd
                                      ---------------------------------
                                   Name:       Calvin R. Boyd
                                      ---------------------------------
                                   Title:      Assistant Secretary
                                      ---------------------------------

                                   PULTE DIVERSIFIED COMPANIES, INC.

                                   By:  /s/    Calvin R. Boyd
                                      ---------------------------------
                                   Name:       Calvin R. Boyd
                                      ---------------------------------
                                   Title:      Assistant Secretary
                                      ---------------------------------

                                  PULTE FINANCIAL COMPANIES, INC.


                                   By:  /s/    Calvin R. Boyd
                                      ---------------------------------
                                   Name:       Calvin R. Boyd
                                      ---------------------------------
                                   Title:      Assistant Secretary
                                      ---------------------------------

                             [signatures continued]

<PAGE>   8
                                     PULTE HOME CORPORATION


                                     BY:    /s/Calvin R. Boyd
                                       -----------------------------------------
                                     Name:    Calvin R. Boyd
                                          --------------------------------------
                                     Title:   Assistant Secretary
                                           -------------------------------------


                                     PULTE DEVELOPMENT CORPORATION


                                     BY:    /s/Calvin R. Boyd
                                       -----------------------------------------
                                     Name:    Calvin R. Boyd
                                          --------------------------------------
                                     Title:   Assistant Secretary
                                           -------------------------------------



                                     PULTE HOMES, INC.


                                     BY:    /s/Calvin R. Boyd
                                       -----------------------------------------
                                     Name:    Calvin R. Boyd
                                          --------------------------------------
                                     Title:   Assistant Secretary
                                           -------------------------------------


                                     PULTE HOMES OF GREATER KANSAS CITY, INC.


                                     BY:    /s/Calvin R. Boyd
                                       -----------------------------------------
                                     Name:    Calvin R. Boyd
                                          --------------------------------------
                                     Title:   Assistant Secretary
                                           -------------------------------------


                                     PULTE HOME CORPORATION OF MASSACHUSETTS


                                     BY:    /s/Calvin R. Boyd
                                       -----------------------------------------
                                     Name:     Calvin R. Boyd
                                          --------------------------------------
                                     Title:    Assistant Secretary
                                           -------------------------------------

<PAGE>   9
                                     PULTE HOMES OF MICHIGAN CORPORATION


                                     BY:    /s/Calvin R. Boyd
                                       -----------------------------------------
                                     Name:    Calvin R. Boyd
                                          --------------------------------------
                                     Title:   Assistant Secretary
                                           -------------------------------------


                                     PULTE HOMES OF MINNESOTA CORPORATION


                                     BY:    /s/Calvin R. Boyd
                                       -----------------------------------------
                                     Name:    Calvin R. Boyd
                                          --------------------------------------
                                     Title:   Assistant Secretary
                                           -------------------------------------



                                     PULTE HOMES OF OHIO CORPORATION


                                     BY:    /s/Calvin R. Boyd
                                       -----------------------------------------
                                     Name:    Calvin R. Boyd
                                          --------------------------------------
                                     Title:   Assistant Secretary
                                           -------------------------------------


                                     PULTE HOME CORPORATION OF TEXAS


                                     BY:    /s/Calvin R. Boyd
                                       -----------------------------------------
                                     Name:    Calvin R. Boyd
                                          --------------------------------------
                                     Title:   Assistant Secretary
                                           -------------------------------------


                                     SEAN\CHRISTOPHER HOMES, INC.


                                     BY:    /s/Calvin R. Boyd
                                       -----------------------------------------
                                     Name:    Calvin R. Boyd
                                          --------------------------------------
                                     Title:   Assistant Secretary
                                           -------------------------------------

<PAGE>   10
                                     PULTE LIFESTYLE COMMUNITIES, INC.


                                     BY:    /s/Calvin R. Boyd
                                       -----------------------------------------
                                     Name:     Calvin R. Boyd
                                          --------------------------------------
                                     Title:    Assistant Secretary
                                          --------------------------------------
<PAGE>   11
                                     LENDERS
                                     -------
                                     NATIONSBANK, N.A., IN ITS CAPACITY AS AGENT
                                     AND AS A LENDER

                                     BY:    /s/Wallace Harris, Jr.
                                       -----------------------------------------
                                     Name:     WALLACE W. HARRIS, JR.
                                          --------------------------------------
                                     Title:    VICE PRESIDENT
                                           -------------------------------------


<PAGE>   12
                                     COMERICA BANK, in its capacity
                                     as Co-Agent and as a Lender


                                     BY:    /s/Hugh G. Porter
                                       -----------------------------------------
                                     Name:     Hugh G. Porter
                                          --------------------------------------
                                     Title:    VICE PRESIDENT
                                           -------------------------------------
<PAGE>   13
                                     THE FIRST NATIONAL BANK OF CHICAGO,
                                     in its capacity as Co-Agent and as
                                     Lender


                                     BY:    /s/Kevin L. Gillen
                                       -----------------------------------------
                                     Name:     Kevin L. Gillen
                                          --------------------------------------
                                     Title:    ASSISTANT VICE PRESIDENT
                                           -------------------------------------
<PAGE>   14
                                     THE BANK OF NEW YORK


                                     BY:    /s/Patricia M. Dominum
                                       -----------------------------------------
                                     Name:     PATRICIA M. DOMINUM
                                          --------------------------------------
                                     Title:    VICE PRESIDENT
                                           -------------------------------------
<PAGE>   15
                                     SUNTRUST BANK


                                     BY:    /s/Roger Shreers
                                       -----------------------------------------
                                     Name:     Roger P. Shreers
                                          --------------------------------------
                                     Title:    Banking Officer
                                           -------------------------------------


                                     BY:    /s/Shelley Browne
                                       -----------------------------------------
                                     Name:     Shelley M. Browne
                                          --------------------------------------
                                     Title:    Vice President
                                           -------------------------------------
<PAGE>   16



                         CREDIT LYONNAIS CHICAGO BRANCH


                         By: /s/  Mary Ann Klemm
                            -----------------------------------
                         Name:    Mary Ann Klemm
                              ---------------------------------
                         Title:   Vice President and Group Head
                              ---------------------------------



                         CREDIT LYONNAISE CAYMAN ISLAND
                         BRANCH


                         By:  s/s Mary Ann Klemm
                            -----------------------------------
                         Name:    Mary Ann Klemm
                              ---------------------------------
                         Title:   Authorized Signature
                               --------------------------------
<PAGE>   17








                                        UNITED STATES NATIONAL BANK OF
                                        OREGON



                                        By: /s/  Monica J. Treacy
                                           ------------------------------
                                        Name:    Monica J. Treacy
                                             ----------------------------
                                        Title:   Assistant Vice President
                                              ---------------------------
<PAGE>   18




                                            THE BANK OF TOKYO-MITSUBISHI LTD.,
                                            CHICAGO BRANCH (f/k/a Bank of Tokyo,
                                            Ltd. Chicago Branch)




                                            By: /s/ Hajime Watanabe
                                                --------------------------------
                                            Name:   Hajime Watanabe
                                                 -------------------------------
                                            Title:  Deputy General Manager
                                                  ------------------------------
<PAGE>   19






                                             MICHIGAN NATIONAL BANK



                                             By: /s/ Jeffrey M. Terrill
                                                 -------------------------------
                                             Name:   Jeffrey M. Terrill
                                                  ------------------------------
                                             Title:  Relationship Manager
                                                   -----------------------------
<PAGE>   20
                                   EXHIBIT A
                                   ---------

                                                                EXHIBIT 2.01A(c)

                        FORM OF SWING LINE LOAN REQUEST

TO:           NATIONSBANK, N.A., as Lender
              100 North Tryon Street
              Charlotte, North Carolina 28255

RE:           Credit Agreement dated as of January 5, 1995 among Pulte
              Corporation (the "Borrower"), NationsBank, N.A., as Agent
              Comerica Bank and The First National Bank of Chicago, as Co-
              Agents and the Lenders party thereto (as amended from to time,
              the "Credit Agreement")

DATE:                        , 199
              ---------------     -

1.       This Swing Line Loan Request is made pursuant to the terms of the
         Credit Agreement.  Capitalized terms used herein and not
         otherwise defined herein shall have the meanings assigned to such
         terms in the Credit Agreement.

2.       Please be advised that the Borrower is requesting a Swing Line Loan,
         and in connection therewith sets forth below the terms on which such
         Swing Line Loan is requested to be made:

         (A)      Date of requested
                  Swing Line Loan                     --------------------------

         (B)      Principal Amount of
                  requested Swing Line Loan           --------------------------

         (C)      Type of Swing Line Loan
                  (Base Rate Loan or Quoted
                  Rate Swing Line Loan)               --------------------------

         (D)      If a Quoted Rate Swing
                  Line Loan, the Interest
                  Period and the last day
                  thereof                             --------------------------


<PAGE>   21
3.       The representations and warranties set forth in Sections 6.01, 6.02,
         6.03, 6.04, 6.05, 6.14, 6.16 and 6.17 of the Credit Agreement are
         true and correct in all material respects as if made on the date
         hereof.

4.       As of the date hereof, no Default or Event of Default has occurred and
         is continuing or would be caused by the requested Swing Line Loan.

                                             Very truly yours,

                                             PULTE CORPORATION

                                             By:
                                               ---------------------------------
                                             Name:
                                                  ------------------------------
                                             Title
                                                  ------------------------------