<PAGE>   1
                                                                   EXHIBIT 10.12



                       THIRD LOAN MODIFICATION AGREEMENT


         This THIRD LOAN MODIFICATION AGREEMENT ("Agreement") is made and
entered into as of this 4th day of March, 1997, by and between SUNRISE ASSISTED
LIVING LIMITED PARTNERSHIP, a Virginia limited ("Borrower") and GREAT OAK, LLC,
a Delaware Limited Liability Company ("Lenders").

                                    RECITALS

         A.  Lender is the owner of the indebtedness (the "Loan") evidenced by
that certain Amended and Restated Promissory Note dated June 6, 1996, executed
by Borrower in favor of General Electric Capital Corporation ("GECC") in the
principal face amount of $87,000,000 (the "Amended Note")

         B.  The Loan is secured, in part, by mortgages and deeds of trust
executed by Borrower listed on Schedule 1 attached hereto (as heretofore
amended, modified and assigned, individually a "Mortgage" and collectively, the
"Mortgages"), encumbering the real property and improvements legally described
on Exhibit "A" attached hereto.

         C.  The Mortgages and the other documents and instruments executed from
time to time in connection with the Loan, as amended from time to time, are
collectively referred to herein as the "Loan Documents".

         D.  The Loan Documents were heretofore amended pursuant to the terms of
that certain First Loan Modification Agreement dated as of February 15, 1996
and that certain Second Loan Modification Agreement dated as of May l, 1996,
both executed by Borrower and GECC.

         E.  Borrower and Lender have agreed to modify certain terms and
provisions of the Amended Note.

         NOW, THEREFORE in consideration of the foregoing, and other good and
valuable consideration, the receipt and sufficiency of which is hereby
acknowledged, the parties agree as follows:

                                   AGREEMENT

         1.  The foregoing recitals are hereby incorporated by reference herein.

         2.  All initially capitalized terms not otherwise defined herein shall
have the respective meanings ascribed to them in the Amended Note.

         3.  Effective March 4, 1997, the term "Class B Contract Index Rate ",
as used in the Amended Note, shall mean, with respect to the Class B
Indebtedness, the rate of interest equal to one and three-quarters percent
(1.75%) per annum in excess of the Libor Rate;
<PAGE>   2
provided, however, that to and including March 3, 1997, the Class B Contract
index Rate shall be equal to three and three-quarters percent (3.75%) per annum
in excess of the Libor Rate.

         4.  From and after March 4, 1997 to and including March 3, 1999, the
Class B Indebtedness may not be prepaid, in whole or in part; provided,
however, that if at any time during the period March 4, 1998 to and including
March 3, 1999, the Libor Rate increases to more than 5.9375% (the "Increase"),
repayment of the whole or part of the Class B Indebtedness during the period
commencing thirty (30) days from the effective date of the Increase, to and
including sixty (60) days from the effective date of the Increase, shall be
permitted. From and after March 4, 1999, to and including the Maturity Date,
the provisions of the Amended Note, including without limitation, Section 6B.
thereof, shall govern prepayment of the Class B Indebtedness.

         5.  Nothing contained herein shall be in construed as in any manner
modifying that certain letter agreement dated December 30, 1996 executed by
Lender and Borrower, a copy of which is attached hereto as Exhibit B.

         6.  Except as modified herein, the terms and provisions of the Amended
Note remain unchanged and in full force and effect.  In the event of any
conflict or inconsistencies between the terms of the Amended Note or any of the
other Loan Documents and the terms of this Agreement, the terms of this
Agreement shall govern and control. Except as expressly modified or replaced
pursuant to the terms of or as contemplated by this Agreement, the Loan
Documents are in full force and effect and are hereby ratified and confirmed by
Borrower and Lender.

         7.  This Agreement shall be binding upon and inure to the benefit of
Lender and Borrower, and their respective heirs, legal representatives,
successors and assigns subject to all limitations set forth in the Loan
Documents. This Agreement is not intended to benefit any party other than the
Borrower, the Lender, and the successors and assigns of the Lender and is
specifically not intended to be for the benefit of any party other than those
which are a party to this Agreement.

         8.  This Agreement may be executed in two or more counterparts, each of
which may be executed by one or more of the parties hereto, but all of which,
when taken together, shall constitute but one agreement.

         9.  The validity, meaning and effect of this Agreement shall be
determined in accordance with the laws of the Commonwealth of Virginia
applicable to contracts made to be performed in that State without regard to
principles of conflicts of law.

         10. Borrower's (and its partners') liability hereunder is limited as
set forth in Section 17 of the Amended Note and Section 17 of the Amended Note
is hereby incorporated by reference as if fully set forth herein.
<PAGE>   3
         IN WITNESS WHERE OF, the parties hereto have executed this document
as of the day and year first above written

                               Borrower:

                               SUNRISE ASSISTED LIVING LIMITED
                               PARTNERSHIP, a Virginia limited partnership

                               By: Sunrise Assisted Living Investments, Inc.
                                   A Virginia corporation its general partner



                                       By:   /s/ David W. Faeder
                                           ------------------------------------
                                           David W. Faeder,
                                           Executive Vice-President




                                       By:   /s/ Thomas B. Newell
                                           ------------------------------------
                                           Thomas B. Newell,
                                           Executive Vice-President




                               Lender

                               GREAT OAK LLC, a Delaware limited
                               liability company

                               By: GE Capital Realty Group, Inc., a
                                     Texas corporation, its
                                     attorney-in-fact


                                       By: /s/ Joseph E. Jernigan
                                           ------------------------------------
                                           Its: Vice President
                                           ------------------------------------


Prepared by and after recording return to:

James B. Fadim, Esq.
Sonnenschein Nath & Rosenthal
8000 Sears Tower
Chicago, Illinois 60606-6404
(312) 876-7971
<PAGE>   4
COMMONWEALTH OF VIRGINIA   )
                           ) SS:
COUNTY OF FAIRFAX          )

         Before me, a Notary Public, in and for said County, in the Commonwealth
aforesaid, personally appeared David W. Faeder and Thomas B. Newell , the
Executive Vice-Presidents of SUNRISE ASSISTED LIVING INVESTMENTS, INC., a
Virginia corporation, the general partner of SUNRISE ASSISTED LIVING LIMITED
PARTNERSHIP, a Virginia limited partnership, and acknowledge the execution of
the foregoing instrument on behalf of the corporation, as such general partner.

         WITNESS my hand and Notarial Seal this 4 day of March, 1997


                                              /s/ Mellissa A. Haynes
                                            -----------------------------------
                                            Signature

                                              Mellissa A. Haynes
                                            -----------------------------------
                                            Printed Name


My Commission Expires.:

----------------------------
 March 31, 2000


STATE OF TEXAS   )
                 ) SS.
COUNTY OF DALLAS )

         I, the undersigned, a Notary Public, in and for said County and State,
DO HEREBY CERTIFY, that Joseph D Jernigan, personally known to me to be Vice
President of GE CAPITAL REALTY GROUP, INC., a Texas corporation, acting as
attorney-in-fact for GREAT OAK, TLC, a Delaware limited liability company,
appeared before me this day in person and acknowledged that he signed and
delivered the said instrument as the free and voluntary act of corporation, as
said attorney-in-fact, for the uses and purposes therein set forth.

         GIVEN under my hand and Notarial Seal this 4 day of March, 1997.



                                            -----------------------------------
                                            Signature

                                                     /s/ Tonya J. Havland
                                            -----------------------------------
                                            Printed Name Tonya J. Havland

My Commission Expires:
 October 14, 1998
----------------------------

<PAGE>   5
                        CONSENT OF SUNRISE TERRACE, INC.
                      TO THIRD LOAN MODIFICATION AGREEMENT

         Capitalized terms used herein without definition shall have the
respective meanings ascribed thereto in the Amended and Restated Note dated June
6, 1996, executive by Sunrise Assisted Living limited Partnership in favor of
General Electric Capital Corporation.

         The undersigned, as Guarantor pursuant to the Guaranty, hereby
consents and agrees to all of the terms and conditions of the above and
foregoing Third Loan Modification agreement dated as of March 4, 1997, and
hereby remakes all of the covenants made and reaffirms all of the obligations to
be performed by the undersigned as Guarantor under the Guaranty. The undersigned
acknowledges and reaffirms that it remains liable under the Guaranty and that
the Guaranty is in full force and effect.

DATED: As of March 4, 1997

                                 SUNRISE TERRACE, INC. a Virginia corporation



                                 By:        /s/ David W. Faeder
                                     -----------------------------------------
                                     David W. Faeder, Executive Vice-President


                                 By:        /s/ Thomas B. Newell
                                     -----------------------------------------
                                     Thomas B. Newell, Executive Vice-President
<PAGE>   6
COMMONWEALTH OF VIRGINIA   )
                           ) SS:
COUNTY OF FAIRFAX          )



         I, the undersigned, a Notary Public, in and for said County, in the
Commonwealth aforesaid, DO HEREBY CERTIFY, that David W. Faeder and Thomas B.
Newell, personally known to me to be the Executive Vice-Presidents of Sunrise
Terrace, inc., a Virginia corporation appeared before me this day in person and
acknowledged that he signed and delivered the said instrument as the free and
voluntary act of said corporation, for the uses and purposes therein set forth.

         GIVEN under my hand and Notarial Seal, this 4 day of March, 1997.


                                            /s/ Mellissa A. Haynes
                                            -----------------------------------
                                            Signature


                                                Mellissa A. Haynes
                                            -----------------------------------
                                            Printed Name

My Commission Expires:
March 31, 2000
----------------------------
<PAGE>   7
                             CONSENT OF INDEMNITORS

         Capitalized terms used herein without definition shall have the
respective meanings ascribed there to in the Amended and Restated Note dated
June 6, 1996, executed by Sunrise Assisted Living Limited Partnership in favor
of General Electric Capital Corporation.

         Each of the undersigned, an indemnitor under the Indemnity Agreement
and Hazardous Substance Indemnity both dated June 8, 1994 and executed in
connection with the Loan, hereby acknowledges and consents to the execution of
the above and foregoing Third Loan Modification Agreement dated as of March 4,
1997, and agrees that the terms and conditions thereof shall not modify, amend,
affect, or diminish any of the obligations or liabilities of the indemnitors
under the Indemnity Agreement or under the Hazardous Substance Indemnity
Agreement.

DATED: As of March 4, 1997


/s/ Paul J. Klaassen                              /s/ Teresa M. Klaassen
---------------------------                      ---------------------------
Paul J. Klaassen                                 Teresa M. Klaassen



COMMONWEALTH OF VIRGINIA   )
                           ) SS.
COUNTY OF FAIRFAX          )

         Before me, a Notary Public, in and for said County and in the
Commonwealth aforesaid, personally appeared Paul J. Klaassen and Teresa
Klaassen, and acknowledged their execution of the foregoing instrument.

         WITNESS my hand and Notarial Seal this 3 day of March, 1997.


                                                 /s/ Mellissa A. Haynes
                                                 ---------------------------
                                                 Signature


                                                 Mellissa A. Haynes
                                                 ---------------------------
                                                 Printed Name


My Commission Expires:
March 31, 2000
----------------------------