<PAGE>
                                                                  Exhibit 10.31


                        FIRST AMENDMENT TO LOAN AGREEMENT


     THIS FIRST AMENDMENT TO LOAN AGREEMENT (this "Amendment"), is made as of
July 7, 1995 by and between  THE PRUDENTIAL INSURANCE COMPANY OF AMERICA, a New
Jersey corporation ("Lender") and REAL ESTATE INVESTMENT TRUST OF CALIFORNIA, a
California real estate investment trust ("Borrower").

                                    RECITALS:

     A.  Lender has made a loan to Borrower in the original principal amount of
$55,000,000, which loan is governed by that certain Loan Agreement dated as of
January 31, 1994 by and between Borrower and Lender (the "Loan Agreement") and
evidenced by that certain Promissory Note dated as of January 31, 1994 executed
by Borrower in favor of Lender (the "Note").

     B.  Borrower and Lender have agreed to modify and amend the Loan Agreement
as provided herein.

     NOW, THEREFORE, in consideration of the foregoing and for other good and
valuable consideration the receipt and sufficiency of which are hereby
acknowledged by Borrower, Borrower and Beneficiary hereby agree as follows:


                                   AGREEMENT:

    1.  DEFINITIONS.  All capitalized terms used in this Amendment, unless
otherwise defined, shall have the meanings given thereto in the Loan Agreement.

    2.  AMENDMENTS TO LOAN AGREEMENT.  Borrower and Lender agree that the Loan
Agreement shall be amended as provided in this Paragraph 2.

    2.1.  Section 1.1 of the Loan Agreement shall be amended by replacing the
definition of Approved Indebtedness, in its entirety, with the following revised
definition therefor:

               "APPROVED INDEBTEDNESS" means collectively, (i) this
          Loan, (ii) the 955 Prudential Loan, (iii) the Sanwa Line of
          Credit (including amounts borrowed thereunder after the
          Closing Date in compliance with the terms hereof), (iv) the
          Union Line of Credit (including amounts borrowed thereunder
          after the Closing Date in compliance with the terms hereof),
          (v) the Tango Loan, (vi) debt incurred in the ordinary
          course of business to acquire goods, supplies, services or
          merchandise on normal trade credit, (vii) surety bonds which
          are obtained in the ordinary course of business, and
          (ix) Capital Lease Obligations in an amount not to exceed,
          at any time, $1,000,000; provided, however, that in any and
          all events, such Approved Indebtedness shall be subject to,
          and included within the calculations relating to, the
          financial covenants set forth in Section 6.9 hereof.   

    2.2.  Section 1.1 of the Loan Agreement shall be amended by replacing the
definition of Approved Liens, in its entirety, with the following revised
definition therefor:

               "APPROVED LIENS" means the Sanwa Liens, the Prudential
          Liens, the Union Liens, the Tango Lien, and liens for real
          property taxes described in Section 6.2(i) hereof.

    2.3.  Section 1.1 of the Loan Agreement shall be amended by replacing the
definition of Debt Service Coverage, in its entirety, with the following revised
definition therefor:


<PAGE>

               "DEBT SERVICE COVERAGE"  means, with respect to any
          period of Net Operating Income being measured, the ratio, as
          calculated by Lender, of (a) Net Operating Income for the
          applicable period, to (b) the sum of (i) the interest
          payments on the Loan for such period, (ii) the interest
          payments on the 955 Prudential Loan for such period
          (excluding, when applicable, the Amortization Payments), and
          (iii) the interest payments and all regularly scheduled
          principal amortization payments on all other Indebtedness
          for such period (collectively, "Debt Service").

    2.4.  Section 1.1 of the Loan Agreement shall be amended by adding the
following definition to be inserted therein in alphabetical order:

               "PRUDENTIAL LIENS" means the Liens on the Secured
          Facilities (as defined in the 955 Loan Documents) provided
          by the Deeds of Trust (as defined in the 955 Loan Documents)
          as security for the 955 Prudential Loan.

    2.5.  Section 1.1 of the Loan Agreement shall be amended by replacing the
definition of Sanwa Line of Credit, in its entirety, with the following revised
definition therefor:

               "SANWA LINE OF CREDIT" means that certain secured line
          of credit established by Sanwa Bank California ("Sanwa
          Bank") in favor of Borrower which is secured by the Sanwa
          Liens, and any replacement line(s) of credit therefor which
          comply with the provisions of Section 6.12 hereof.

    2.6.  Section 1.1 of the Loan Agreement shall be amended by adding the
following definition to be inserted therein in alphabetical order:

               "TANGO LIEN" means the lien on the Tango Apartments
          located in Las Vegas, Nevada (the "Tango Property"), created
          by the deed of trust in favor of Lincoln National Life
          Insurance Company with respect to the Tango Loan.

    2.7.  Section 1.1 of the Loan Agreement shall be amended by adding the
following definition to be inserted therein in alphabetical order:

               "TANGO LOAN" means the first mortgage loan in the
          principal amount of approximately $4,261,320 (as of March
          31, 1995) made by Lincoln National Life Insurance Company, 
          which loan was assumed by Borrower and is secured by the
          Tango Lien.

    2.8.  Section 1.1 of the Loan Agreement shall be amended by adding the
following definitions at the end of Section 1.1:

               "955 LOAN DOCUMENTS" means the "Loan Documents" as
          defined in the 955 Loan Agreement.

               "955 PRUDENTIAL LOAN" means that certain $18,000,000 term loan
          made by Lender to Borrower under Loan No. 6-100-955 as described in
          that certain Loan Agreement dated as of July 7, 1995 by and between
          Lender and Borrower, as amended from time to time (the "955 Loan
          Agreement").

    2.9.  Section 5.7.B(ii) of the Loan Agreement shall be amended, in its


                                      2


<PAGE>

entirety, to provide as follows:

          (ii) on or before July 24, 1995, repay, in full, the Union
          Line of Credit and cause the Union Property to be reconveyed
          as security therefor, and on or before July 27, 1995, and
          continually thereafter, cause the outstanding balance of the
          Sanwa Line of Credit to be not greater than $18,500,000;
          provided, however, that after the Closing Date, Borrower
          shall, subject to the terms hereof, be entitled to repay
          such indebtedness and draw on such line of credit in
          accordance with the terms thereof as long as the outstanding
          principal balance thereof does not exceed, at any time,
          $18,500,000.



















                                      3


<PAGE>

    2.10. A new Section 5.12 of the Loan Agreement shall be added thereto and
shall provide, in its entirety, as follows:

               5.12 OBTAIN/MAINTAIN RATING.

               On or before December 31, 1996, Borrower will obtain, and shall
          thereafter always maintain in effect, a rating for the long-term
          unsecured debt of Borrower from Standard & Poor's Rating Group, Moody
          Investor Services, Fitch Investor Services, Duff & Phelps or any other
          nationally recognized rating agency approved by Lender (an "Approved
          Rating Agency"). Borrower shall pay all of the fees, costs and
          expenses incurred in connection with obtaining and maintaining such
          rating.


    2.11. Section 6.8 of the Loan Agreement shall be amended, in its entirety,
to provide as follows:

               6.8  OTHER DEBT.    

                    Other than (i) the Approved Indebtedness and (ii) unsecured
          Indebtedness of Borrower incurred after the Closing Date and which, in
          any and all events, strictly complies with the terms of this Agreement
          (including, without limitation,  Section 6.9 hereof ("New Unsecured
          Indebtedness")), Borrower and the Consolidated Partnership shall not
          have outstanding any Indebtedness or create, assume, suffer to exist
          or incur any Indebtedness or lease obligations (other than the Loan
          and the 955 Prudential Loan from Lender and the leasing of its
          headquarters in the ordinary course of business), or become liable for
          the indebtedness of another, without the prior written consent of
          Lender. Prior to incurring any New Unsecured Indebtedness, Borrower
          shall notify Lender of the terms and conditions thereof and shall
          certify to Lender in writing that the incurring of such unsecured debt
          does not violate any Restrictions (as defined in the 955 Loan
          Agreement). Borrower agrees to disclose the existence of this
          Section 6.8 in writing to any lender/creditor other than a
          lender/creditor holding Approved Indebtedness (excluding therefrom a
          new replacement lienholder of any Approved Lien in substitution for
          the existing holder of such Approved Lien).  In the event Borrower at
          any time defaults in the performance or observance of this
          Section 6.8, then notwithstanding the terms of any such financing
          between Borrower and such other lender/creditor, the indebtedness of
          such other lender/creditor shall be junior and subordinate in payment
          and application to the indebtedness evidenced hereby and by the Note.

    2.12. Section 6.9.C of the Loan Agreement shall be amended, in its entirety,
to provide as follows:

               C.  MAXIMUM SECURED DEBT.  Borrower and the Consolidated
          Partnership shall not create, incur, suffer or allow to exist
          Indebtedness secured in whole or in part by any of its properties
          (including, without limitation, the Facilities) or other assets
          (including, with respect to the Sanwa Line of Credit and the Union
          Line of Credit, only the funded portion of such line of credit
          indebtedness within the calculation of secured Indebtedness)  which at
          any time (i) exceeds the lesser of (a) (x) $40,800,000 or (y) twenty
          percent (20%) of Consolidated Book Value, or (ii) is secured, in whole
          or in part, by any assets or properties of Borrower or the
          Consolidated Partnership, other than the Secured Facilities (until the
          Unsecured Conversion Date (as defined in the 955 Loan Agreement)
          occurs), the Tango Property, the Sanwa


                                      4


<PAGE>

          Properties, and the Union Property.

    2.13. Section 6.12 of the Loan Agreement shall be amended, in its entirety,
to provide as follows:

               6.12  NO CHANGE IN COLLATERAL FOR LINES OF CREDIT.

                    Borrower shall not, without the prior written consent of
          Lender, change, substitute or otherwise modify the make-up, mix or
          nature of the Sanwa Properties or any other property securing the
          Sanwa Line of Credit or the make-up, mix or nature of the Union
          Property or any other property securing the Union Line of Credit;
          provided, however, that Borrower shall be entitled to (i) replace
          either the Sanwa Line of Credit and/or the Union Line of Credit with a
          new line of credit or lines of credit from one or more institutional
          lenders as long as (x) the terms thereof comply with the provisions of
          this Agreement (including, without limitation, Section 6.9 hereof) and
          (y) the only property serving as collateral or security for such line
          of credit or lines of credit is the Sanwa Properties and/or the Union
          Property or (ii) pay-off the Union Line of Credit in full by
          increasing the amounts available under the Sanwa Line of Credit to
          $18,500,000, adding the Union Property as collateral for the Sanwa
          Line of Credit, and using the proceeds of the increased Sanwa Line of
          Credit to repay in full the Union Line of Credit. At no time shall the
          aggregate amount available under the Sanwa Line of Credit and the
          Union Line of Credit exceed $18,500,000.
















                                      5


<PAGE>

    2.14. Section 7.2.A of the Loan Agreement shall be amended, in its entirety,
to provide as follows:

               A.  FAILURE TO MAKE PAYMENTS.  Failure of Borrower or
          the Consolidated Partnership to pay when due any principal
          or interest on any Indebtedness (including, without
          limitation, the Tango Loan, the Sanwa Line of Credit or the
          Union Line of Credit) (other than Indebtedness referred to
          in Section 7.1 and Section 7.2.C) or Contingent Obligation;
          or

    2.15. Section 7.2.B of the Loan Agreement shall be amended, in its entirety,
to provide as follows:

               B.  BREACH OF ANY MATERIAL TERM.  Breach or default of Borrower
          or the Consolidated Partnership with respect to any other material
          term of (i) any evidence of any Indebtedness or Contingent Obligation
          (ii) any loan agreement, mortgage, indenture or other agreement
          relating thereto, if the effect of such failure, default or breach is
          to cause, or to permit the holder or holders of that Indebtedness or
          Contingent Obligation (or a trustee on behalf of such holder or
          holders) then to cause, that Indebtedness or Contingent Obligation to
          become or be declared due prior to its stated maturity (or the stated
          maturity of any underlying obligation, as the case may be); or

    2.16. A new Section 7.2.C of the Loan Agreement shall be added thereto and
shall provide, in its entirety, as follows:

               C.   DEFAULT UNDER 955 PRUDENTIAL LOAN.  Any default,
          Event of Default or Potential Event of Default under or as
          defined in any of the 955 Loan Documents; or

    2.17. Section 7.5 of the Loan Agreement shall be amended, in its entirety,
to provide as follows:


               7.5  OTHER DEFAULTS UNDER AGREEMENT OR LOAN DOCUMENTS.

                    Borrower shall default in the performance of or
          compliance with any term contained in this Agreement or in
          the performance or compliance with any term contained in the
          other Loan Documents (other than the occurrence of an event
          of default otherwise specifically described in Sections 7.1,
          7.2.C, 7.3, 7.4, 7.6, or 7.7 hereof, which shall not have
          any additional cure periods hereunder) and such default
          shall not have been remedied within thirty (30) days after
          the occurrence of such default; or

    2.18. Section 7.12.A of the Loan Agreement shall be amended, in its
entirety, to provide as follows:

               A.  Any Person shall have (i) acquired beneficial ownership
          (within the meaning of Rule 13d-3 of the Securities and Exchange
          Commission under the Securities Exchange Act of 1934) directly or
          indirectly, of shares or securities of Borrower (or other securities
          convertible into such securities), or (ii)  acquired by contract or
          otherwise, or shall have entered into a contract or arrangement which
          upon consummation will result in its acquisition of or control over
          shares or securities of Borrower (or other


                                      6


<PAGE>

          securities convertible into such securities), in either case, 
          representing ten percent (10%) or more of the outstanding shares or
          securities of Borrower; or

    2.19. Section 7.13 of the Loan Agreement shall be amended, in its entirety,
to provide as follows:

          7.13 MATERIAL ADVERSE CHANGE.

               The occurrence of a Material Adverse Change; or

    2.20. A new Section 7.14 of the Loan Agreement shall be added thereto and
shall provide, in its entirety, as follows:

          7.14 FAILURE TO OBTAIN/MAINTAIN RATING.

               On and after December 31, 1996, Borrower shall have failed to
          obtain or maintain a rating for the long-term unsecured debt of
          Borrower from an Approved Rating Agency;

    2.21. Section 8.3 of the Loan Agreement shall be amended such that any
reference therein to "Indemnities" shall be a reference to "Indemnitee."

    2.22. EXHIBIT A to the Loan Agreement shall be replaced with SCHEDULE ONE
attached hereto.

    2.23. EXHIBIT B to the Loan Agreement shall be replaced with SCHEDULE TWO
attached hereto.

    2.24. EXHIBIT F to the Loan Agreement shall be replaced with an update
thereto attached as SCHEDULE THREE hereto.











                                      7


<PAGE>

3.  REPRESENTATIONS AND WARRANTIES.  Borrower makes the following 
representations and warranties to Lender all of which are material and are 
made to induce Lender to enter into this Amendment.

               3.1.  All representations and warranties in the Loan Documents
               were true, accurate and complete in every material respect as of
               the date made and are true, accurate and complete in every
               respect as of the date hereof, and do not fail to disclose any
               material fact necessary to make the representations not
               misleading.

               3.2.  Borrower has full power, legal capacity and authority to
               execute and deliver this Amendment.

               3.3.  This Amendment has been duly authorized, executed and
               delivered by Borrower.

4.  NO OTHER MODIFICATIONS. Except as provided herein, the Loan Agreement 
shall remain unchanged and in full force and effect.

5.  GOVERNING LAW.  This Amendment shall be governed by and construed in 
accordance with the laws of the State of California.

6.  SEVERABILITY.  If any term, provision, covenant or condition of this 
Amendment or any application thereof should be held by a court of competent 
jurisdiction to be invalid, void or unenforceable, all terms, provisions, 
covenants and conditions hereof and all applications thereof not held 
invalid, void or unenforceable shall continue in full force and effect and 
shall in no way be affected, impaired or invalidated thereby.

7.  SUCCESSOR AND ASSIGNS.  The provisions of this Amendment shall be binding 
upon and inure solely to the benefit of Lender and Borrower, and their 
respective heirs, legal representatives, successors and assigns.

8.  COUNTERPARTS.  This Amendment may be executed in any number of 
counterparts and by different parties hereto on separate counterparts, each 
of which counterparts, when so executed and delivered, shall be deemed to be 
an original, and all of which counterparts, taken together, shall constitute 
but one and the same Amendment.

                                      8


<PAGE>

          IN WITNESS WHEREOF, Borrower and Lender have caused this Amendment to
be executed as of the day and year first above written.


                                       BORROWER:

                                       REAL ESTATE INVESTMENT TRUST OF
                                       CALIFORNIA, a California real
                                       estate investment trust


                                       By:____________________________________
                                           Jay W. Pauly
                                           President


                                       By:____________________________________
                                           Leroy E. Carlson
                                           Vice President


                                       LENDER:

                                       THE PRUDENTIAL INSURANCE COMPANY 
                                       OF AMERICA


                                       By:____________________________________
                                       Its:___________________________________






<PAGE>

                                       SCHEDULE ONE

                                         EXHIBIT A



                                  COMPLIANCE CERTIFICATE



The Prudential Insurance
  Company of America
Four Embarcadero Center, Suite 2700
San Francisco, California  94111
Attention:  Regional Counsel

Gentlemen:

               I, the undersigned, the _________________________ of Real Estate
Investment Trust of California, a California real estate investment trust
("Borrower"), do hereby certify, represent and warrant as follows: 

          1.   This Certificate is furnished pursuant to [Section 3.1.L]
[Section 5.1.A.[(i)][(ii)]] of that certain Loan Agreement dated as of January
31, 1994 (the "Loan Agreement", the terms defined therein being used herein as
therein defined) by and between Borrower and The Prudential Insurance Company of
America, a New Jersey corporation ("Lender").

          2.   SCHEDULE 1 attached hereto sets forth financial data and
computations evidencing the Borrower's compliance with Section 6.9 of the Loan
Agreement, all of which data and computations are complete, true and correct. 

          3.   No Event of Default or Potential Event of Default under the Loan
Agreement or the other Loan Documents has occurred and is continuing. 

          4.   The representations and warranties set forth in Article 4 of the
Loan Agreement are true and correct as of the date hereof as though made on and
as of the date hereof.

          5.   The total credit commitments relating to, and the principal
balance of, all Indebtedness of the Borrower and the Consolidated Partnership as
of ___________ __, 19__ are as follows:

          Lender/Creditor     Committed Amount       Principal Balance
          ---------------     ----------------       -----------------

          Prudential          $55,000,000             $_____________
          955 Prudential
               Loan           $18,000,000             $18,000,000
          Sanwa               $__________             $_____________
          Union               $__________             $_____________
          Tango Loan          $ 4,300,000             $_____________
          _______________                             $_____________
          _______________                             $_____________

          6.   The total credit commitments relating to, and the principal
balance of, all secured Indebtedness of the Borrower and the Consolidated
Partnership as of ___________ __, 19__ are as follows:


          Lender/Creditor     Committed Amount       Principal Balance
          ---------------     ----------------       -----------------


          Prudential (955)     $18,000,000            $18,000,000
          Sanwa                $__________            $_____________
          Union                $__________            $_____________


<PAGE>

          Tango Loan           $ 4,300,000            $_____________


               The only properties and/or assets serving as security for secured
Indebtedness of the Borrower and the Consolidated Partnership are the Secured
Facilities, the Sanwa Properties, the Union Property, and the Tango Property.


          7.   The total credit commitments relating to, and the principal
balance of, all unsecured Indebtedness of the Borrower and the Consolidated
Partnership as of ___________ __, 19__ are as follows:

          Lender/Creditor     Committed Amount       Principal Balance
          ---------------     ----------------       -----------------


          Prudential           $55,000,000            $_____________
          _______________                             $_____________
          _______________                             $_____________



          Executed this ____ day of _____________, 19__. 



                                                                               
                                    ___________________________________________

                                    Name: _____________________________________

                                    Title:_____________________________________


<PAGE>

                                   Schedule 1
                                       To
                             Compliance Certificate

                For the _____________ Ended ______________, 19__


SECTION 6.9.A TANGIBLE NET WORTH                                  ($ Thousands)


A.   Consolidated Book Value:

       (i)  Facilities (net of accumulated
            depreciation), PLUS                                     $___________

      (ii)  Cash, PLUS                                              $___________

     (iii)  Permitted Investments, PLUS                             $___________

      (iv)  Prepaid Expenses, PLUS                                  $___________

       (v)  Equity interest in Unconsolidated
            Partnership (net of Borrower's pro rata
            share of Unconsolidated Partnership's
            secured indebtedness), PLUS                             $___________

      (vi)  Leasehold Projects (sum of
            (A)(1), and (2))                                        $___________

            (1)  aggregate book value of
                 Finance Leases, PLUS                               $___________

            (2)  aggregate book value of all
                 outstanding Existing Purchase
                 Money Mortgages not in default                     $___________

     (vii)  Consolidated Book Value (sum of
            (A)(i) through (A)(vi), inclusive)                      $___________

B.   Consolidated total liabilities of
     Borrower and the Consolidated Partnership:                     $___________

C.   Tangible Net Worth (A(vii)-B):                                 $___________

D.   MINIMUM TANGIBLE NET WORTH ($ THOUSANDS):                          $100,000


<PAGE>

SECTION 6.9.B INDEBTEDNESS TO CONSOLIDATED
BOOK VALUE                                                         ($ Thousands)


A.   Indebtedness:                                                  $___________

B.   Consolidated Book Value
     (from A(vi) above):                                            $___________

C.   Indebtedness to Consolidated
      Book Value (A/B):                                               ____: 1.00

D.   MAXIMUM INDEBTEDNESS TO CONSOLIDATED
     BOOK VALUE:                                                       .50: 1.00


SECTION 6.9.C MAXIMUM SECURED DEBT                                 ($ Thousands)


A.   Secured Indebtedness:                                          $___________

B.   MAXIMUM SECURED INDEBTEDNESS -
     ((i) $40,800 ($ THOUSANDS) OR (ii) 20% OF 
     CONSOLIDATED BOOK VALUE (FROM A(vi) ABOVE):                    $___________


<PAGE>

SECTION 6.9.D. DEBT SERVICE COVERAGE                               ($ Thousands)

(All figures are for the period from
___________ __, 19__ to ____________ __, 19__,
inclusive)

A.   Net Operating Income:

       (i)  gross income derived from Facilities,
            PLUS                                                    $___________

      (ii)  earnings derived from cash and
                cash equivalents, PLUS                              $___________

     (iii)  net earnings derived from Unconsolidated
                Partnership Interest, PLUS                          $___________

      (iv)  net rent from Leasehold Projects, PLUS                  $___________

       (v)  interest payments on Existing Purchase
                Money Mortgages not in default                      $___________

      (vi)  Gross Income (sum of (i) through (v))                   $___________

     (vii)  Operating Expenses                                      $___________

    (viii)  Administrative Expenses                                 $___________

      (ix)  Net Operating Income ((vi)-((vii)+(viii))               $___________

B.   Debt Service

       (i)  Interest payments on Loan:                              $___________

      (ii)  Interest payments on all
           other Indebtedness:                                      $___________

     (iii)  Debt Service ((i)+(ii))                                 $___________

C.   Debt Service Coverage Ratio ((A)(viii)/B(iii))                  ____ to 1.0

D.   MAXIMUM DEBT SERVICE COVERAGE RATIO:                             2.5 TO 1.0


<PAGE>


                                      SCHEDULE TWO

                                       Exhibit B

                                  [Sanwa Properties]


1.   Parkglen Apartments

2.   Windrush Apartments

3.   Skypark Professional Building

4.   Valencia Medical Center

5.   PSICOR Building


<PAGE>

                                     SCHEDULE THREE

                                       Exhibit F

                                 [Existing Facilities]