<PAGE>
                                                                    EXHIBIT 10.1

               FIRST AMENDMENT TO MASTER CREDIT FACILITY AGREEMENT

         THIS FIRST AMENDMENT TO MASTER CREDIT FACILITY AGREEMENT (this
"AMENDMENT") is made as of the 29th day of August, 2002 by (i)(a) SUN SECURED
FINANCING LLC, a Michigan limited liability company, (b) ASPEN - FT. COLLINS
LIMITED PARTNERSHIP, a Michigan limited partnership and (c) SUN SECURED
FINANCING HOUSTON LIMITED PARTNERSHIP, a Michigan limited partnership
(collectively, "BORROWER"), and (ii) ARCS COMMERCIAL MORTGAGE CO., L.P., a
California limited partnership, its successors, transferees and assigns
("LENDER").

                                    RECITALS

         A. Pursuant to that certain Master Credit Facility Agreement dated as
of May 29, 2002 (the "MASTER AGREEMENT") Borrower and Lender agreed to the terms
and conditions under which Lender would establish a credit facility in the
original amount of $101,760,000 and make Advances to Borrower.

         B. All of the Lender's right, title and interest in the Master
Agreement and the Loan Documents executed in connection with the Master
Agreement or the transactions contemplated by the Master Agreement have been
assigned to Fannie Mae pursuant to that certain Assignment of Collateral
Agreements and Other Loan Documents, dated as of May 29, 2002 (the
"ASSIGNMENT"). Fannie Mae has not assumed any of the obligations of the Lender
under the Master Agreement or the Loan Documents as a result of the Assignment.
Fannie Mae has designated the Lender as the servicer of the Advances
contemplated by the Master Agreement.

         C. The parties are executing this Amendment pursuant to the Master
Agreement to reflect (i) the addition of five (5) Mortgaged Properties commonly
known as Academy/West Point in Michigan, Autumn Ridge Estates in Iowa, King's
Court in Michigan and Timberline Estates in Michigan to the Collateral Pool,
(ii) an increase in the Variable Facility Commitment as set forth hereinafter,
(iii) a decrease in the maximum amount by which the Commitment may be increased,
and (iv) revise certain terms and conditions of the Master Agreement as set
forth hereinafter.

         NOW, THEREFORE, the parties hereto, in consideration of the mutual
promises and agreements contained in this Amendment and the Master Agreement,
and other good and valuable consideration, the receipt and sufficiency of which
is hereby acknowledged, hereby agree as follows:

         SECTION 1. ADDITION OF MORTGAGED PROPERTY. The Mortgaged Properties
commonly known as Academy/West Point, Autumn Ridge Estates, King's Court and
Timberline Estates are hereby added to the Collateral Pool under the Master
Agreement.

         SECTION 2. EXHIBIT A Exhibit A to the Master Agreement is hereby
deleted and replaced with the Exhibit A attached to this Amendment.





<PAGE>
         SECTION 3. EXPANSION. The Variable Facility Commitment shall be
increased by $37,667,500 and the definition of Commitment is hereby replaced in
its entirety with the following new definition:

                  "Variable Facility Commitment" means an aggregate amount of
         $139,427,500, which shall be evidenced by the Variable Facility Note in
         the form attached hereto as Exhibit C, plus such amount as Borrower may
         elect to add to the Variable Facility Commitment in accordance with
         Article 4, less such amount as Borrower may elect to convert from the
         Variable Facility Commitment to the Fixed Facility Commitment in
         accordance with Section 1.08, and less such amount by which Borrower
         may elect to reduce the Variable Facility Commitment in accordance with
         Article. V

         SECTION 4. MAXIMUM AMOUNT OF INCREASE IN COMMITMENT. The increase in
the Commitment will decrease the maximum amount of increase as set forth in
Section 4.01(a) of the Master Agreement and that provision is hereby deleted
from the Master Agreement and replaced in its entirety by the following:

         Section 4.01(a). Maximum Amount of Increase in Commitment. The maximum
         amount by which the Commitment may be increased is $60,572,500.

         SECTION 5. SPECIAL COVENANTS REGARDING KING'S COURT. The Parties are
aware that certain phases of the Additional Mortgaged Property commonly known as
King's Court in Traverse City, Michigan are not connected to the municipal water
system. Borrower hereby covenants, represents and warrants that in the event
that the water supplied to these phases is not in compliance with the
requirements of any Governmental Authority, and such non-compliance is not cured
by Borrower within ten (10) days, Borrower will at its sole cost and expense
hook up and connect all phases to the municipal water system within thirty (30)
days of receiving notice from Lender of such requirement; provided that, if
action is commenced and diligently pursued by Borrower within such 30 days, then
Borrower shall have an additional thirty (30) days or, if longer, the time
permitted by the Governmental Authority to comply with such requirement.

         SECTION 6. EXTENSION OF DATE TO PROVIDE CAP IN LIEU OF GUARANTY.
Section 15.01(a) is hereby amended by deleting the date "August 29, 2002" and
inserting the date "October 31, 2002" in lieu thereof.

         SECTION 7. CAPITALIZED TERMS. All capitalized terms used in this
Amendment which are not specifically defined herein shall have the respective
meanings set forth in the Master Agreement.

         SECTION 8. FULL FORCE AND EFFECT Except as expressly modified by this
Amendment, all terms and conditions of the Master Agreement shall continue in
full force and effect.

         SECTION 9. COUNTERPARTS. This Amendment may be executed in counterparts
by the parties hereto, and each such counterpart shall be considered an original
and all such counterparts shall constitute one and the same instrument.



                                       2
<PAGE>

         SECTION 10. APPLICABLE LAW. The provisions of Section 17.06 of the
Master Agreement (entitled "Choice of Law; Consent to Jurisdiction; Waiver of
Jury Trial") are hereby incorporated into this Amendment by this reference to
the fullest extent as if the text of such provisions were set forth in their
entirety herein.

         IN WITNESS WHEREOF, the parties hereto have executed this Amendment as
of the day and year first above written.

              BORROWER:

              SUN SECURED FINANCING LLC, a Michigan limited
              liability company

              By:       Sun Communities Operating Limited Partnership, a
                        Michigan limited partnership, its Sole Member

                        By:      Sun Communities, Inc, a Maryland
                                 corporation, its General Partner

                        By:      /s/ Jonathan M. Colman
                            ------------------------------------------------
                        Name:    Jonathan M. Colman
                        Title:  Senior Vice President - Acquisitions


              ASPEN - FT. COLLINS LIMITED PARTNERSHIP, a
              Michigan limited partnership

              By:       Sun GP L.L.C., a Michigan limited liability
                        company, its General Partner

                        By:      Sun Communities, Inc., a Maryland
                                 Corporation, its Manager


                                 By:        /s/ Jonathan M. Colman
                                     --------------------------------------
                                 Name:      Jonathan M. Colman
                                 Title:     Senior Vice President - Acquisitions

              SUN SECURED FINANCING HOUSTON LIMITED
              PARTNERSHIP, a Michigan limited partnership

              By:       Sun Secured Financing GP, Inc., a Michigan
                        corporation, its General Partner

                        By:      /s/ Jonathan M. Colman
                            ------------------------------------------------
                        Name:    Jonathan M. Colman
                        Title:   Senior Vice President - Acquisitions



                                       3
<PAGE>

              LENDER:

              ARCS COMMERCIAL MORTGAGE CO., L.P., a
              California limited partnership

              By:       ACMC Realty, Inc., a California
                        Corporation, its General Partner



                        By:      /s/ Timothy L. White
                            ------------------------------------------------
                        Name:    Timothy L. White
                        Title:   Chief Operating Officer






                                       4
<PAGE>
                                    EXHIBIT A

                    SCHEDULE OF INITIAL MORTGAGED PROPERTIES
                        INITIAL VALUES AND INITIAL VALUES

<TABLE>
<CAPTION>
PROPERTY NAME                        PROPERTY ADDRESS                                             INITIAL VALUE
------------------------------------ ------------------------------------------------------------ ---------------------
<S>                                  <C>                                                          <C>
Allendale                            11400 Boyne Boulevard, Allendale, MI 49401                   $11,575,000
Presidential Estates                 5075 Presidential Lane, Hudsonville, MI 49426                $12,100,000
Meadow Lake                          3951 Brentwood Cir. W., White lake, MI 48383                 $18,800,000
White Oak                            4084 West Stanley Road, Mt. Morris, MI 48458                 $13,800,000
BrooksideManor                       61108 C.R. 17, Goshen, IN 46526                              $16,500,000
Valley Brook                         4620 South High School Road, Indianapolis, IN 46234          $26,000,000
Branch Creek                         12609 Dessau Road, Austin, TX 78754                          $12,000,000
Chisolm Point                        900 Broken Feather Trail, Pflugerville, TX 78660             $12,500,000
Pin Oak                              8001 Oakhave Drive, O'Fallon, MO 63366                       $13,100,000
Timber Ridge                         3717 S. Taft Hill Dr., Ft. Collins, CO 80526                 $20,200,000
Academy/West Point                   41021 Old Michigan Avenue, Canton, MI 48188                  $16,100,000
Autumn Ridge Estates                 2050 Four Seasons Drive, Ankeny, IA 50021                    $12,650,000
King's Court                         2988 Lafranier Road, Traverse City, MI 49686                 $20,600,000
Timberline Estates                   260 Pin Oak Drive, Coopersville, MI 49404                    $ 8,600,000
</TABLE>