EXHIBIT 10.13

                       EXCEPTIONS TO NON-RECOURSE GUARANTY


         This EXCEPTIONS TO NON-RECOURSE  GUARANTY (this  "Guaranty") is entered
into as of December  15,  2000,  by HUB REALTY  COLLEGE  PARK I, LLC, a Maryland
limited  liability company (the  "Guarantor"),  for the benefit of MERRILL LYNCH
MORTGAGE LENDING, INC., a Delaware corporation (together with its successors and
assigns, the "Lender").


                                    RECITALS

         A. Franklin  Plaza Property  Trust,  a Maryland real estate  investment
trust (the "Borrower") has requested and Lender has agreed to make a loan in the
principal  amount of $44,000,000  (the "Loan"),  pursuant to a Loan and Security
Agreement,  dated of even date herewith (as amended,  modified or restated,  the
"Loan Agreement"), between Borrower and Lender which Loan will be evidenced by a
Promissory Note, dated of even date herewith (as amended,  modified,  renewed or
restated,  and any replacement notes therefor,  collectively,  the "Note"), from
Borrower to Lender and secured by, among other things, a Mortgage, Assignment of
Leases and Rents,  Security  Agreement  and Fixture  Filing,  dated of even date
herewith  (as  amended,   modified,   restated,  spread  or  consolidated,   the
"Instrument"),  encumbering certain real property located at One Franklin Plaza,
Philadelphia,  Pennsylvania,  as more  particularly  described in the Instrument
(the "Property"). As used herein, the term "Loan Documents" shall mean the Note,
the  Instrument,  and any other  documents or  instruments  given by Borrower or
others and  accepted by Lender for the  purposes  of  evidencing,  securing,  or
guaranteeing  the  Loan,  each  as  amended  or  modified  from  time  to  time.
Capitalized  terms  used  but  not  otherwise  defined  herein  shall  have  the
respective meanings given thereto in the Loan Agreement.

         B. Guarantor will derive substantial  benefits from Lender's making the
Loan to Borrower.

         C. As a condition to making the Loan to Borrower,  Lender requires that
Guarantor execute this Guaranty.

         NOW, THEREFORE, in order to induce Lender to make the Loan to Borrower,
and in consideration thereof, Guarantor agrees as follows:

         1. As used herein, the term  "Indebtedness"  shall mean all obligations
evidenced by the Note or secured by the Instrument.

         2.  Guarantor  hereby  absolutely,   unconditionally   and  irrevocably
guarantees to Lender the full and prompt  payment when due,  whether at maturity
or earlier, by reason of acceleration or otherwise, and at all times thereafter,
and  the  full  and  prompt  performance  when  due,  of all  of  the  following
(collectively, the "Guaranteed Obligations"):
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         (a)      All amounts for which  Borrower is liable under Article XII of
                  the Loan Agreement; and

         (b)      All costs and expenses,  including  reasonable fees and out of
                  pocket expenses of attorneys and expert witnesses, incurred by
                  Lender in enforcing its rights under this Guaranty.

For purposes of  determining  Guarantor's  liability  under this  Guaranty,  all
payments  made by  Borrower  with  respect to the  Indebtedness  and all amounts
received by Lender from the enforcement of its rights under the Instrument shall
be applied first to the portion of the  Indebtedness  for which neither Borrower
nor Guarantor have personal liability.

Guarantor  hereby  promises  to pay and  perform,  as and when due  (whether  by
acceleration,  at maturity, or otherwise) and at all times thereafter,  each and
all of the items and obligations which are stated to be guaranteed hereunder but
which  are  obligations  for  which  Guarantor  is  primarily  liable or are not
obligations of others.  Guarantor  hereby agrees that any such sums shall accrue
interest  at the  Default  Rate  until paid if not paid as and when due and that
such sums,  together with any accrued interest  thereon,  shall become a part of
Guarantor's obligations hereunder.

         3. The  obligations of Guarantor  under this Guaranty shall survive any
foreclosure  proceeding,  any foreclosure sale, any delivery of any deed in lieu
of foreclosure, and any release of record of the Instrument.

         4.   Guarantor's   obligations   under  this  Guaranty   constitute  an
unconditional guaranty of payment and not merely a guaranty of collection.

         5. The  obligations of Guarantor under this Guaranty shall be performed
without  demand  by  Lender  and  shall  be  unconditional  irrespective  of the
genuineness,   validity,  regularity  or  enforceability  of  any  of  the  Loan
Documents,  and without regard to any other  circumstance  which might otherwise
constitute a legal or equitable discharge of a surety or a guarantor.  Guarantor
shall be liable even if Borrower  had no  liability  at the time of execution of
the Loan Documents,  or thereafter ceases to be liable.  Guarantor hereby waives
the benefit of all  principles  or  provisions  of law,  statutory or otherwise,
which are or might be in  conflict  with the terms of this  Guaranty  and agrees
that Guarantor's obligations shall not be affected by any circumstances, whether
or not referred to in this Guaranty, which might otherwise constitute a legal or
equitable  discharge of a surety or a  guarantor.  Guarantor  hereby  waives the
benefits  of any right of  discharge  under any and all  statutes  or other laws
relating  to  guarantors  or  sureties  and any  other  rights of  sureties  and
guarantors  thereunder.  Without  limiting  the  generality  of  the  foregoing,
Guarantor hereby waives,  to the fullest extent  permitted by law,  diligence in
collecting  the  Indebtedness,  presentment,  demand for payment,  protest,  all
notices  with respect to the Note,  this  Guaranty,  or any other Loan  Document
which may be required by statute,  rule of law or otherwise to preserve Lender's
rights against  Guarantor  under this Guaranty,  including,  but not limited to,
notice of acceptance,  notice of any amendment of the Loan Documents,  notice of
the  occurrence  of any  default,  notice  of intent  to  accelerate,  notice of
acceleration,  notice of dishonor, notice of foreclosure, notice of protest, and
notice of the incurring by Borrower of any obligation or indebtedness. Guarantor
also  waives,  to the fullest  extent  permitted  by law,  following an Event of
Default,  all rights to require  Lender to (a) proceed  against  Borrower or any


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other  guarantor  of  Borrower's  payment  or  performance  with  respect to the
Indebtedness (an "Other Guarantor"), (b) if Borrower or any Other Guarantor is a
partnership,  proceed  against  any  general  partner of  Borrower  or the Other
Guarantor,  (c)  proceed  against or exhaust  any  collateral  held by Lender to
secure the repayment of the Indebtedness,  or (d) pursue any other remedy it may
now or hereafter have against  Borrower,  or if Borrower is a  partnership,  any
general partner of Borrower.

         6. Guarantor  understands that the exercise by Lender of certain rights
and remedies  contained in the  Instrument  (such as a  nonjudicial  foreclosure
sale) may affect or eliminate  Guarantor's right of subrogation against Borrower
and that  Guarantor may therefore  incur a partially or totally  nonreimbursable
liability under this Guaranty.  Nevertheless,  Guarantor  hereby  authorizes and
empowers Lender to exercise,  in its sole and absolute discretion,  any right or
remedy, or any combination thereof, which may then be available, since it is the
intent and purpose of Guarantor that its  obligations  under this Guaranty shall
be absolute,  independent  and  unconditional  under any and all  circumstances.
Guarantor  expressly  waives any defense  (which  defense,  if Guarantor had not
given  this  waiver,  Guarantor  might  otherwise  have) to a  judgment  against
Guarantor by reason of a judicial or nonjudicial  foreclosure.  Without limiting
the generality of the foregoing,  Guarantor  hereby expressly waives any and all
benefits under any applicable law which, if Guarantor had not given this waiver,
(i) would otherwise limit Guarantor's  liability after a foreclosure sale to the
difference between the obligations of Guarantor under this Guaranty and the fair
market value of the property or interests sold at such  nonjudicial  foreclosure
sale, (ii) would otherwise limit Lender's right to recover a deficiency judgment
after a foreclosure  sale, and (iii) would  otherwise  require Lender to exhaust
all of  its  security  before  a  personal  judgment  could  be  obtained  for a
deficiency.  Notwithstanding  any  foreclosure  of the  lien of the  Instrument,
whether by the exercise of the power of sale contained in the Instrument,  by an
action for judicial  foreclosure or by Lender's  acceptance of a deed in lieu of
foreclosure,  Guarantor shall remain bound under this Guaranty. Guarantor waives
all rights and defenses that Guarantor may have because  Borrower's  obligations
are secured by real property. This means, among other things:

                  (i)  Lender  may  collect   from   Guarantor   without   first
foreclosing on any real or personal property  collateral  pledged by Borrower or
others; and

                  (ii) If  Lender  forecloses  on any real  property  collateral
pledged by Borrower or others: (a) the amount of the debt may be reduced only by
the price for which that collateral is sold at the foreclosure sale, even if the
collateral  is worth more than the sale price;  and (b) Lender may collect  from
Guarantor even if Lender,  by foreclosing on the real property  collateral,  has
destroyed any right Guarantor may have to collect from Borrower.

This is an unconditional and irrevocable  waiver of any rights and defenses that
Guarantor may have because Borrower's obligations are secured by real property.

         7. Guarantor also waives any right or defense based upon an election of
remedies by Lender,  even though such election  (e.g.,  nonjudicial  foreclosure
with  respect  to any  collateral  held by  Lender to  secure  repayment  of the
Indebtedness)  destroys or otherwise impairs the subrogation rights of Guarantor
or the right of  Guarantor  (after  payment  of the  obligations


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guaranteed by Guarantor  under this  Guaranty) to proceed  against  Borrower for
reimbursement, or both.

         8. Guarantor  shall have no right to assert or exercise,  or attempt to
assert or exercise,  and hereby  waives any right to assert or attempt to assert
any claim for,  subrogation,  reimbursement,  indemnification,  and contribution
against Borrower and against any general partner, member or other constituent of
Borrower,  and against any other  person or any  collateral  or security for the
Indebtedness, until the Indebtedness has been indefeasibly paid and satisfied in
full, and there has expired the maximum possible period  thereafter during which
any  payment  made  by  Borrower  or  others  to  Lender  with  respect  to  the
Indebtedness  could be deemed a preference  under the United  States  Bankruptcy
Code.

         9. At any time or from time to time,  without  notice to Guarantor  and
without affecting the liability of Guarantor for the Guaranteed Obligations, (a)
the time for payment of the principal of or interest on the  Indebtedness may be
extended or the  Indebtedness  may be renewed in whole or in part;  (b) the time
for  Borrower's  performance  of or  compliance  with any  covenant or agreement
contained in the Note,  the Loan  Agreement,  the  Instrument  or any other Loan
Document,  whether  presently  existing  or  hereinafter  entered  into,  may be
extended or such  performance or compliance  may be waived;  (c) the maturity of
the Indebtedness may be accelerated as provided in the Note, the Loan Agreement,
the  Instrument,  or any other Loan Document;  (d) the Note, the Loan Agreement,
the Instrument,  or any other Loan Document may be modified or amended by Lender
and Borrower in any respect,  including,  but not limited to, an increase in the
principal  amount;  and (e) any security for the  Indebtedness  may be modified,
exchanged,  surrendered  or otherwise  dealt with or additional  security may be
pledged or mortgaged for the Indebtedness.

         10. Any indebtedness of Borrower held by Guarantor now or in the future
is and shall be subordinated to the  Indebtedness  and any such  indebtedness of
Borrower shall be collected,  enforced and received by Guarantor, as trustee for
Lender,  but  without  reducing  or  affecting  in any manner the  liability  of
Guarantor under the other provisions of this Guaranty.

         11. If any payment by Borrower is held to constitute a preference under
any  applicable  bankruptcy,  insolvency,  or similar  laws, or if for any other
reason Lender is required to refund any sums to Borrower,  such refund shall not
constitute a release of any liability of Guarantor  under this  Guaranty.  It is
the intention of Lender and Guarantor that  Guarantor's  obligations  under this
Guaranty  shall not be  discharged  except by  Guarantor's  performance  of such
obligations and then only to the extent of such performance.

         12.  Lender may assign its rights  under this  Guaranty  in whole or in
part and upon any such assignment, all the terms and provisions of this Guaranty
shall inure to the benefit of such assignee to the extent so assigned. The terms
used to  designate  any of the  parties  herein  shall be deemed to include  the
heirs, legal  representatives,  successors and assigns of such parties;  and the
term "Lender" shall include,  in addition to Lender, any lawful owner, holder or
pledgee of the Note.

         13. This  Guaranty  and the other Loan  Documents  represent  the final
agreement  between the parties and may not be contradicted by evidence of prior,
contemporaneous  or

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subsequent oral agreements.  There are no unwritten oral agreements  between the
parties.    All   prior   or   contemporaneous    agreements,    understandings,
representations,  and statements, oral or written, are merged into this Guaranty
and the other Loan Documents. Guarantor acknowledges that it has received copies
of the Note and all other Loan  Documents.  Neither this Guaranty nor any of its
provisions may be waived, modified, amended, discharged, or terminated except by
an agreement in writing signed by the party against which the enforcement of the
waiver, modification,  amendment,  discharge, or termination is sought, and then
only to the extent set forth in that agreement.

         14. THIS  GUARANTY  SHALL BE GOVERNED  BY, AND SHALL BE  CONSTRUED  AND
ENFORCED IN ACCORDANCE WITH, THE INTERNAL LAWS OF THE STATE OF NEW YORK, WITHOUT
REGARD TO CONFLICTS OF LAWS PRINCIPLES.

         15. This Guaranty has been duly  authorized,  executed and delivered by
Guarantor  and  constitutes  the  valid and  binding  obligation  of  Guarantor,
enforceable  against  Guarantor  in  accordance  with its  terms.  No  approval,
consent,   order  or  authorization   of  any  governmental   authority  and  no
designation, registration, declaration or filing with any governmental authority
is required in  connection  with the  execution and delivery of this Guaranty by
Guarantor.  Guarantor  has no  defense  or  offset  to the  enforcement  of this
Guaranty.  The  execution  and  delivery  of this  Guaranty  will not violate or
contravene  in any way the articles of  incorporation  or bylaws or  partnership
agreement,  articles of organization or operating agreement, as the case may be,
of Guarantor or any indenture,  agreement or instrument to which  Guarantor is a
party or by which it or its  property  may be  bound,  or be in  conflict  with,
result  in a breach  of or  constitute  a  default  under  any  such  indenture,
agreement or other instrument, result in the creation or imposition of any lien,
charge or  encumbrance  of any nature  whatsoever  upon any of the  property  or
assets  of  Guarantor,  except as  contemplated  by the  provisions  of the Loan
Documents, and no action or approval with respect thereto by any third person is
required.

         16.  GUARANTOR  AND LENDER  EACH (A) AGREE NOT TO ELECT A TRIAL BY JURY
WITH  RESPECT TO ANY ISSUE  ARISING  OUT OF THIS  GUARANTY  OR THE  RELATIONSHIP
BETWEEN THE PARTIES AS  GUARANTOR  AND LENDER THAT IS TRIABLE OF RIGHT BY A JURY
AND (B)  WAIVES  ANY RIGHT TO TRIAL BY JURY WITH  RESPECT  TO SUCH  ISSUE TO THE
EXTENT THAT ANY SUCH RIGHT EXISTS NOW OR IN THE FUTURE.  THIS WAIVER OF RIGHT TO
TRIAL BY JURY IS SEPARATELY GIVEN BY EACH PARTY,  KNOWINGLY AND VOLUNTARILY WITH
THE BENEFIT OF COMPETENT LEGAL COUNSEL.

         17.  Guarantor hereby agrees that, (a) at all times while this Guaranty
is in effect (measured on a quarterly basis), it shall be required to maintain a
net worth (calculated in accordance with GAAP) of not less than $25,000,000 (the
"Minimum  Net Worth  Amount")  exclusive  of the capital  evidenced  by the HRPT
Demand Note  (hereinafter  defined) and (b) in  addition,  until the third (3rd)
anniversary  of the  date  hereof  (the  "Note  Expiration  Date"),  it shall be
required to maintain  additional capital in the amount of $10,000,000  evidenced
by a demand note of even  principal  amount (the "HRPT  Demand  Note") from HRPT
Properties  Trust, a Maryland real estate  investment  trust  (together with its
successors and assigns, "HRPT"), to

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Guarantor.  In the  event  that  Guarantor's  net  worth  shall be less than the
Minimum  Net Worth  Amount  as of the end of any  calendar  quarter  or the HRPT
Demand Note shall be released or terminated (except upon payment in full thereof
in cash by HRPT) prior to the Note  Expiration  Date,  same shall  constitute an
Event of Default hereunder and under the Loan Agreement unless (in the case of a
breach of the net worth covenant only) within thirty (30) days after the earlier
of (a) the date of delivery of Guarantor's financial statements for such quarter
pursuant  to Section  5.1(A)(iii)  of the Loan  Agreement  and (b) the date that
Guarantor  has  knowledge  that its net worth as of the end of such  quarter was
less than the Minimum Net Worth Amount:

                  (i)   Guarantor   shall   effect  a   Guarantor   Substitution
(hereinafter  defined)  pursuant to which a Replacement  Guarantor  (hereinafter
defined)  shall assume all of  Guarantor's  obligations  under this  Guaranty in
accordance with the terms and conditions of Section 18; or

                  (ii) Guarantor shall deliver to Lender cash or an irrevocable,
unconditional  clean sight draft letter of credit issued by a bank, and in form,
reasonably acceptable to Lender (and which shall either be an "evergreen" letter
of credit or have a term  expiring not less than thirty (30) Business Days after
the Maturity  Date) (a "Letter of Credit") in an amount equal to the  difference
(the "Net Worth  Deficiency")  between (A) the Minimum Net Worth  Amount and (B)
Guarantor's  net  worth  as  indicated  in the  applicable  quarterly  financial
statements.  Lender,  in its sole discretion,  may require Guarantor to increase
such  cash  deposit  or  Letter  of  Credit  to the  extent  that the Net  Worth
Deficiency continues to decline in subsequent  quarters.  Such cash or Letter of
Credit will only be released to Guarantor when Guarantor's net worth exceeds the
Minimum Net Worth Amount for four (4) consecutive calendar quarters and provided
no Event of Default has occurred and is continuing. If not sooner returned, such
cash or Letter of Credit shall be returned to Guarantor  upon payment in full of
the Loan and all other obligations by Borrower on the Maturity Date. Any cash or
Letter  of  Credit  provided  under  this  Section  17  shall  be  security  for
Guarantor's obligations hereunder.

         18. Guarantor,  upon at least thirty (30) days notice to Lender,  shall
have the one-time right, to transfer all of its obligations  under this Guaranty
and under that certain  Environmental  Indemnity  Agreement,  dated of even date
herewith  (the  "Environmental   Indemnity")  to  a  replacement   guarantor  (a
"Replacement  Guarantor")  and have such  Replacement  Guarantor  assume  all of
Guarantor's  obligations  hereunder (including compliance with the provisions of
Section 17 hereof) and thereunder  (such transfer and  assumption,  a "Guarantor
Substitution")  provided  and upon the  conditions  with  respect  to each  such
Guarantor Substitution that:

                  (i) No Event of Default shall have occurred and be continuing;

                  (ii) Guarantor shall have delivered  current annual  financial
statements and quarterly financial statements for the Replacement  Guarantor for
the four (4) most  recent  calendar  quarters  satisfying  the  requirements  of
Sections 5.1(A)(i) and (iii), respectively,  of the Loan Agreement and submitted
to Lender true, correct and complete copies of any and all other information and
documents of any kind reasonably  requested by Lender concerning the Replacement
Guarantor and all of such financial  statements and other  information  shall be
acceptable to Lender;

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                  (iii)  Guarantor shall have obtained and delivered to Lender a
Rating Confirmation with respect to the Guarantor Substitution;

                  (iv)  Guarantor  shall  have paid all of  Lender's  reasonable
costs and expenses (including,  without limitation,  reasonable  attorney's fees
and  disbursements)  in connection with  considering and effecting the Guarantor
Substitution,  and the preparation,  negotiation,  execution and delivery of any
and all  documents  and  agreements  required by Lender in  connection  with the
Guarantor Substitution;

                  (v) The  Replacement  Guarantor's  net  worth as of the end of
each of the  most  recent  four  (4)  calendar  quarters  (as  indicated  on the
financial  statements  delivered  under clause (ii) above) shall equal or exceed
the Minimum Net Worth  Amount and the  financial  condition  of the  Replacement
Guarantor  shall  otherwise  be  satisfactory  to Lender in its sole good  faith
discretion;

                  (vii) The Replacement  Guarantor shall execute and deliver any
and all documents reasonably required by Lender in connection with the Guarantor
Substitution, each in form and substance reasonably acceptable to Lender;

                  (viii) Counsel to the  Replacement  Guarantor shall deliver to
Lender opinions in form and substance  satisfactory to Lender as to such matters
as Lender and the Rating Agencies shall  reasonably  require,  which may include
opinions as to  substantially  the same matters as were required with respect to
Guarantor in connection  with the  origination  of the Loan  including,  without
limitation, a bankruptcy non-consolidation opinion;

                  (ix) In the event  such  Guarantor  Substitution  shall  occur
prior to the Note  Expiration  Date,  Guarantor shall transfer and assign all of
its  right,  title  and  interest  in the HRPT  Demand  Note to the  Replacement
Guarantor (or HRPT shall deliver a new demand note to the Replacement  Guarantor
in the amount of $10,000,000);

                  (x)  Guarantor  shall not be permitted to effect more than two
(2) Guarantor  Substitutions  during any twenty-four (24) month period and shall
not be permitted to effect more than three (3)  Guarantor  Substitutions  during
the entire term of the Loan.

         19.  This  Guaranty  shall not be  secured  by the  Property,  the Loan
Documents,  or any other  collateral  of any nature  which is  security  for the
Obligations. Without limitation, this Section 19 has priority over any provision
in this Guaranty or any of the other Loan Documents which states or implies that
the this Guaranty is so secured.

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         IN WITNESS WHEREOF,  Guarantor has executed and delivered this Guaranty
as of the date first written above.

                                     GUARANTOR:


                                     HUB REALTY COLLEGE PARK I, LLC,
                                     a Maryland limited liability company


                                     By:  /s/ John A. Mannix
                                          Name: John A. Mannix
                                          Title: President