<PAGE>   1
                                                                   EXHIBIT 10.42

                                    GUARANTY

                  GUARANTY (as the same may be amended, supplemented or
otherwise modified from time to time, this "GUARANTY"), dated as of March 7,
2000, by and among each of the Subsidiaries listed on Schedule I hereto
(collectively, the "SUBSIDIARY GUARANTORS") and FLEET NATIONAL BANK, as
administrative agent (in such capacity, the "ADMINISTRATIVE AGENT") on behalf of
the Lenders under and as defined in the Loan Agreement (hereinafter defined).

                                    RECITALS

         I. Reference is made to the Term Loan Agreement, dated as of the date
hereof, by and among New Plan Excel Realty Trust, Inc., a Maryland corporation,
the Lenders party thereto, and the Administrative Agent (as the same may be
amended, supplemented or otherwise modified from time to time, the "LOAN
AGREEMENT").

         II. The Administrative Agent and the Lenders have made it a condition
precedent to the effectiveness of the Loan Agreement that each Subsidiary
Guarantor execute and deliver this Guaranty.

         III. Each Subsidiary Guarantor expects to derive substantial benefit
from the Loan Agreement and the transactions contemplated thereby and, in
furtherance thereof, has agreed to execute and deliver this Guaranty.

         Therefore, in consideration of the Recitals, the terms and conditions
herein contained and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, each of the Subsidiary Guarantors,
the Borrower and the Administrative Agent hereby agree as follows:

         1.       DEFINED TERMS

                  (a)      Capitalized terms used herein which are not otherwise
                           defined herein shall have the respective meanings
                           ascribed thereto in the Loan Agreement.

                  (b)      When used in this Guaranty, the following capitalized
                           terms shall have the respective meanings ascribed
                           thereto as follows:

                           "BORROWER OBLIGATIONS" means all present and future
obligations and liabilities, whether deemed principal, interest, additional
interest, fees, expenses or otherwise of the Borrower to the Administrative
Agent and the Lenders, including, without limitation, all obligations under (i)
the Loan Agreement, (ii) the Notes and (iii) all other Loan Documents.

                                       1
<PAGE>   2

                           "GUARANTOR OBLIGATIONS" means, with respect to each
Subsidiary Guarantor, all of the obligations and liabilities of such Subsidiary
Guarantor hereunder, whether fixed, contingent, now existing or hereafter
arising, created, assumed, incurred or acquired.

         2.       GUARANTEE

                  (a) Subject to Section 2(b), each Subsidiary Guarantor hereby
absolutely, irrevocably and unconditionally guarantees the full and prompt
payment when due (whether at stated maturity, by acceleration or otherwise) of
the Borrower Obligations. The agreements of each Subsidiary Guarantor in this
Guaranty constitute a guarantee of payment, and no Credit Party shall have any
obligation to enforce any Loan Document or exercise any right or remedy with
respect to any collateral security thereunder by any action, including making or
perfecting any claim against any Person or any collateral security for any of
the Borrower Obligations prior to being entitled to the benefits of this
Guaranty. The Administrative Agent may, at its option, proceed against the
Subsidiary Guarantors, or any one or more of them, in the first instance, to
enforce the Guarantor Obligations without first proceeding against the Borrower
or any other Person, and without first resorting to any other rights or
remedies, as the Administrative Agent may deem advisable. In furtherance hereof,
if any Credit Party is prevented by law from collecting or otherwise hindered
from collecting or otherwise enforcing any Borrower Obligation in accordance
with its terms, such Credit Party shall be entitled to receive hereunder from
the Subsidiary Guarantors after demand therefor, the sums which would have been
otherwise due had such collection or enforcement not been prevented or hindered.

                  (b) Notwithstanding anything to the contrary contained herein,
the maximum aggregate amount of the obligations of each Subsidiary Guarantor
hereunder shall not, as of any date of determination, exceed the lesser of the
greatest amount that is valid and enforceable against such Subsidiary Guarantor
under principles of New York State contract law and the greatest amount that
would not render such Subsidiary Guarantor's liability hereunder subject to
avoidance as a fraudulent transfer or conveyance under Section 548 of Title 11
of the United States Code or any provisions of applicable state law
(collectively, the "FRAUDULENT TRANSFER LAWS"), in each case after giving effect
to all other liabilities of such Subsidiary Guarantor, contingent or otherwise,
that are relevant under the Fraudulent Transfer Laws (specifically excluding,
however, any liability (A) in respect of intercompany indebtedness to the
Borrower or any Affiliate or Subsidiary of the Borrower, to the extent that such
intercompany indebtedness would be discharged to the extent payment is made by
such Subsidiary Guarantor hereunder, and (B) under any guarantee of (1) senior
unsecured indebtedness or (2) indebtedness subordinated in right of payment to
any Borrower Obligation, in either case which contains a limitation as to
maximum liability similar to that set forth in this Section 2(b) and pursuant to
which the liability of such Subsidiary Guarantor hereunder is included in the
liabilities taken into account in

                                       2
<PAGE>   3

determining such maximum liability) and after giving effect as assets to the
value (as determined under the applicable provisions of the Fraudulent Transfer
Laws) of any rights to subrogation, contribution, reimbursement, indemnity or
similar rights of such Subsidiary Guarantor pursuant to applicable law or any
agreement providing for an equitable allocation among such Subsidiary Guarantor
and other Affiliates or Subsidiaries of the Borrower of obligations arising
under guarantees by such parties.

                  (c) Each Subsidiary Guarantor agrees that the Guarantor
Obligations may at any time and from time to time exceed the maximum aggregate
amount of the obligations of such Subsidiary Guarantor hereunder without
impairing this Guaranty or affecting the rights and remedies of any Credit Party
hereunder.

         3.       ABSOLUTE OBLIGATION

                  No Subsidiary Guarantor shall be released from liability
hereunder unless and until the Commitments of the Lenders have terminated and
either (i) the Borrower shall have paid in full the outstanding principal
balance of the Loans, together with all accrued and unpaid interest thereon, and
all other amounts then due and owing under the Loan Documents, or (ii) the
Guarantor Obligations of such Subsidiary Guarantor shall have been paid in full
in cash. Each Subsidiary Guarantor acknowledges and agrees that (a) no Credit
Party has made any representation or warranty to such Subsidiary Guarantor with
respect to the Borrower, any of its Subsidiaries, any Loan Document, or any
agreement, instrument or document executed or delivered in connection therewith,
or any other matter whatsoever, and (b) such Subsidiary Guarantor shall be
liable hereunder, and such liability shall not be affected or impaired,
irrespective of (A) the validity or enforceability of any Loan Document, or any
agreement, instrument or document executed or delivered in connection therewith,
or the collectibility of any of the Borrower Obligations, (B) the preference or
priority ranking with respect to any of the Borrower Obligations, (C) the
existence, validity, enforceability or perfection of any security interest or
collateral security under any Loan Document, or the release, exchange,
substitution or loss or impairment of any such security interest or collateral
security, (D) any failure, delay, neglect or omission by any Credit Party to
realize upon or protect any direct or indirect collateral security,
indebtedness, liability or obligation, any Loan Document, or any agreement,
instrument or document executed or delivered in connection therewith, or any of
the Borrower Obligations, (E) the existence or exercise of any right of set-off
by any Credit Party, (F) the existence, validity or enforceability of any other
guarantee with respect to any of the Borrower Obligations, the liability of any
other Person in respect of any of the Borrower Obligations, or the release of
any such Person or any other guarantor of any of the Borrower Obligations, (G)
any act or omission of any Credit Party in connection with the administration of
any Loan Document or any of the Borrower Obligations, (H) the bankruptcy,
insolvency, reorganization or receivership of, or any other proceeding for the
relief of debtors commenced by or against, any Person, (I) the

                                       3
<PAGE>   4

disaffirmance or rejection, or the purported disaffirmance or purported
rejection, of any of the Borrower Obligations, any Loan Document, or any
agreement, instrument or document executed or delivered in connection therewith,
in any bankruptcy, insolvency, reorganization or receivership, or any other
proceeding for the relief of debtor, relating to any Person, (J) any law,
regulation or decree now or hereafter in effect which might in any manner affect
any of the terms or provisions of any Loan Document, or any agreement,
instrument or document executed or delivered in connection therewith or any of
the Borrower Obligations, or which might cause or permit to be invoked any
alteration in the time, amount, manner or payment or performance of any of the
Borrower's obligations and liabilities (including the Borrower Obligations), (K)
the merger or consolidation of the Borrower into or with any Person, (L) the
sale by the Borrower of all or any part of its assets, (M) the fact that at any
time and from time to time none of the Borrower Obligations may be outstanding
or owing to any Credit Party, (N) any amendment or modification of, or
supplement to, any Loan Document, or (O) any other reason or circumstance which
might otherwise constitute a defense available to or a discharge of the Borrower
in respect of its obligations or liabilities (including the Borrower
Obligations) or of such Subsidiary Guarantor in respect of any of the Guarantor
Obligations (other than by the performance in full thereof).

         4.       REPRESENTATIONS AND WARRANTIES

                  Each of the Subsidiary Guarantors represents and warrants as
to itself that all representations and warranties relating to it contained in
the Loan Agreement are true and correct.

         5.       NOTICES

                  Except as otherwise specifically provided herein, all notices,
requests, consents, demands, waivers and other communications hereunder shall be
in writing (including facsimile) and shall be given in the manner set forth in
Section 11.2 of the Loan Agreement (i) in the case of the Administrative Agent,
to the address set forth in Section 11.2 of the Loan Agreement, (ii) in the case
of a Subsidiary Guarantor, to the address set forth in Schedule I hereto, or
(iii) in the case of each party hereto, to such other addresses as to which the
Administrative Agent may be hereafter notified by the respective parties hereto.

         6.       EXPENSES

                  Each Subsidiary Guarantor agrees that it shall, promptly after
demand, pay to the Administrative Agent any and all reasonable out-of-pocket
sums, costs and expenses, which any Loan Party may pay or incur defending,
protecting or enforcing this Guaranty (whether suit is instituted or not),
reasonable attorneys' fees and disbursements. All sums, costs and expenses

                                       4
<PAGE>   5

which are due and payable pursuant to this Section shall bear interest, payable
on demand, at the highest rate then payable on the Borrower Obligations.

         7.       REPAYMENT IN BANKRUPTCY, ETC.

                  If, at any time or times subsequent to the payment of all or
any part of the Borrower Obligations or the Guarantor Obligations, any Credit
Party shall be required to repay any amounts previously paid by or on behalf of
the Borrower or any Subsidiary Guarantor in reduction thereof by virtue of an
order of any court having jurisdiction in the premises, including as a result of
an adjudication that such amounts constituted preferential payments or
fraudulent conveyances, the Subsidiary Guarantors unconditionally agree to pay
to the Administrative Agent, within 10 days after demand, a sum in cash equal to
the amount of such repayment, together with interest on such amount from the
date of such repayment by such Credit Party to the date of payment to the
Administrative Agent at the applicable after-maturity rate set forth in the Loan
Agreement.

         8.       MISCELLANEOUS

                  (a) Except as otherwise expressly provided in this Guaranty,
each Subsidiary Guarantor hereby waives presentment, demand for payment, notice
of default, nonperformance and dishonor, protest and notice of protest of or in
respect of this Guaranty, the other Loan Documents and the Borrower Obligations,
notice of acceptance of this Guaranty and reliance hereupon by any Credit Party,
and the incurrence of any of the Borrower Obligations, notice of any sale of
collateral security or any default of any sort.

                  (b) No Subsidiary Guarantor is relying upon any Credit Party
to provide to such Subsidiary Guarantor any information concerning the Borrower
or any of its Subsidiaries, and each Subsidiary Guarantor has made arrangements
satisfactory to such Subsidiary Guarantor to obtain from the Borrower on a
continuing basis such information concerning the Borrower and its Subsidiaries
as such Subsidiary Guarantor may desire.

                  (c) Each Subsidiary Guarantor agrees that any statement of
account with respect to the Borrower Obligations from any Credit Party to the
Borrower which binds the Borrower shall also be binding upon such Subsidiary
Guarantor, and that copies of said statements of account maintained in the
regular course of or such Credit Party's business may be used in evidence
against such Subsidiary Guarantor in order to establish its Guarantor
Obligations.

                  (d) Each Subsidiary Guarantor acknowledges that it has
received a copy of the Loan Documents and has approved of the same. In addition,
each Subsidiary Guarantor

                                       5
<PAGE>   6

acknowledges having read each Loan Document and having had the advice of counsel
in connection with all matters concerning its execution and delivery of this
Guaranty.

                  (e) This Guaranty shall be binding upon each Subsidiary
Guarantor and its successors and inure to the benefit of, and be enforceable by
the Administrative Agent, Lenders and their respective successors, transferees
and assigns. No Subsidiary Guarantor may assign any right, or delegate any duty,
it may have under this Guaranty.

                  (f) Subject to the limitations set forth in Section 2(b), the
Guarantor Obligations shall be joint and several.

                  (g) This Guaranty is the "Guaranty" referred to in the Loan
Agreement, and is subject to, and should be construed in accordance with, the
provisions thereof. Each of the parties hereto acknowledges and agrees that the
following provisions of the Loan Agreement are made applicable to this Guaranty
and all such provisions are incorporated by reference herein as if fully set
forth herein, including Sections 1 (Definitions), 2.13 (Taxes; Net Payments),
9.1 (Events of Default), 11.1 (Amendments and Waivers), 11.3 (No Waiver;
Cumulative Remedies), 11.5 (Payment of Expenses and Taxes), 11.7 (Successors and
Assigns), 11.9 (Counterparts), 11.12 (Indemnity), 11.13 (Governing Law), 11.14,
(Headings Description), 11.15 (Severability), 11.16 (Integration), 11.17
(Consent to Jurisdiction), 11.18 (Service of Process), 11.19 (No Limitation on
Service or Suit) and 11.20 (WAIVER OF TRIAL BY JURY) thereof.

                  (h) Each Subsidiary Guarantor agrees that (i) the execution
and delivery of a Guaranty by any Required Additional Guarantor after the date
hereof shall not affect the obligations of the Subsidiary Guarantors hereunder,
and (ii) the Subsidiary Guarantors and each such Required Additional Guarantor
shall, subject to Section 2(b), be jointly and severally liable for all of the
Borrower Obligations.

                  (i) [IF THIS GUARANTY IS BEING EXECUTED BY A REQUIRED
ADDITIONAL GUARANTOR: THE UNDERSIGNED SUBSIDIARY GUARANTOR IS A REQUIRED
ADDITIONAL GUARANTOR AND ACKNOWLEDGES AND AGREES THAT IT IS EXECUTING THIS
GUARANTY IN ACCORDANCE WITH THE REQUIREMENTS OF THE LOAN AGREEMENT IN ORDER TO
INDUCE THE CREDIT PARTIES TO MAKE ADDITIONAL LOANS AND AS CONSIDERATION FOR
LOANS PREVIOUSLY MADE OR ISSUED. THE UNDERSIGNED SUBSIDIARY GUARANTOR AGREES
THAT, SUBJECT TO SECTION 2(b), IT IS JOINTLY AND SEVERALLY LIABLE WITH ALL OTHER
SUBSIDIARIES WHO HAVE PREVIOUSLY EXECUTED AND DELIVERED A GUARANTY PURSUANT TO
THE LOAN AGREEMENT FOR ALL OF THE BORROWER OBLIGATIONS.

                                       6
<PAGE>   7



         IN EVIDENCE of the agreement by the parties hereto to the terms and
conditions herein contained, each such party has caused this Subsidiary
Guarantee to be duly executed on its behalf.

                                      NEW PLAN REALTY TRUST, a
                                      Massachusetts business trust

                                      By:      /s/ Dean Bernstein
                                             ----------------------------------
                                      Name:
                                             ----------------------------------
                                      Title:
                                             ----------------------------------

                                      EXCEL REALTY - ST, INC., a Delaware
                                      corporation

                                      By:      /s/ Dean Bernstein
                                             ----------------------------------
                                      Name:
                                             ----------------------------------
                                      Title:
                                             ----------------------------------

                                             [CORPORATE SEAL]

                                      FLEET NATIONAL BANK, as
                                      Administrative Agent

                                      By:      /s/ Daniel P. Stegemoeller
                                             ----------------------------------
                                      Name:       Daniel P. Stegemoeller
                                             ----------------------------------
                                      Title:      Vice President
                                             ----------------------------------

                                        7
<PAGE>   8

                                   SCHEDULE I
                             TO SUBSIDIARY GUARANTY

                              SUBSIDIARY GUARANTORS

                    UNDER GUARANTY DATED AS OF MARCH 7, 2000


<TABLE>
<CAPTION>
                                    Jurisdiction of Incorporation                      Address for
Name                                or Formation                                       Notices
---------------------               -----------------------------                      --------------------------
<S>                                 <C>                                                <C>
New Plan Realty Trust                 Massachusetts                                     c/o New Plan Excel
                                                                                        Realty Trust, Inc.
                                                                                        1120 Avenue of the Americas
                                                                                        New York, New York  10036

Excel Realty - ST, Inc.               Delaware                                          c/o New Plan Excel
                                                                                        Realty Trust, Inc.
                                                                                        1120 Avenue of the Americas
                                                                                        New York, New York  10036
</TABLE>