<PAGE>

                                                                   Exhibit 10.14

                             SECURED PROMISSORY NOTE
                                     754150

$19,000,000.00                                                 December 20, 2004

1. FOR VALUE RECEIVED, 1025 VERMONT INVESTORS, L.L.C., a Delaware limited
liability company, as "Borrower" (to be construed as "Borrowers" if the context
so requires), hereby promises to pay to the order of PRINCIPAL LIFE INSURANCE
COMPANY, an Iowa corporation (as "Lender"), having a principal place of business
and post office address at do Principal Real Estate Investors, LLC, 801 Grand
Avenue, Des Moines, Iowa 50392-1450, or at such other place as Lender may
designate, the principal sum of Nineteen Million and 00/100 Dollars
($19,000,000.00) (the "Amount" or so much thereof as shall from time to time
have been advanced, together with interest on the unpaid balance of said sum
from December), 2004 (the " Date") at the rate of four and ninety-one
one-hundredths percent (4.91%) per annum.

     A payment of interest from the Closing Date to and including December 31,
2004 shall be paid on the Closing Date calculated by multiplying the actual
number of days elapsed in the period for which interest is being calculated by a
daily rate based on the foregoing annual interest rate and a 360-day year.
Thereafter, interest shall be computed on the unpaid balance on the basis of a
360-day year composed of twelve 30-day months. Beginning on February 1, 2005,
interest shall be due and payable in installments of Seventy-seven Thousand
Seven Hundred Forty-one and 67/100 Dollars ($77,741.67), with an installment in
a like amount due and payable on the same day of each month thereafter
continuing to and including January 1, 2007. Beginning on February 1, 2007,
principal and interest shall be due and payable in installments of One Hundred
Ten Thousand Seventy-eight and 10/100 Dollars ($110,078.10), with an installment
in a like amount due and payable on the same day of each month thereafter until
said principal and interest are fully paid, except that all remaining principal,
interest to and including the date of payment and other Indebtedness shall be
due and payable on January 1, 2010 (the " Date" or such earlier date resulting
from the acceleration of the Indebtedness by Lender. Each installment shall be
credited first upon interest then accrued and the remainder upon principal. All
principal and interest shall be paid in lawful money of the United States of
America by automated clearing house transfer through such bank or financial
institution as shall be approved in writing by Lender, shall be made to an
account designated by Lender, and shall be initiated by Lender or shall be made
in such other manner as Lender may direct from time to time. Any other monthly
deposits or payments Borrower is required to make to Lender under the terms of
the Loan Documents shall be made by the same payment method and on the same date
as the installments of principal and interest due under this Note.

2. No privilege is reserved by Borrower to prepay any principal of this Note
prior to the Maturity Date, except privilege is reserved, after giving thirty
(30) days' prior written notice to Lender, to prepay in full, but not in part,
all principal and interest to and including the date on which payment is made,
along with all sums, amounts, advances, or charges due under any instrument or
agreement by which this Note is secured, upon the payment of a "Whole Premium.
The Make Whole Premium shall be the greater of one percent (1%) of the principal

<PAGE>

amount to be prepaid or a premium calculated as provided in subparagraphs (a)
through (c) below:

     (a)  Determine the "Yield. The Reinvestment Yield will be equal to the
          yield on the * U.S. Treasury Issue ( Issue" published one week prior
          to the date of prepayment and converted to an equivalent monthly
          compounded nominal yield plus 50 basis points. In the event there is
          no market activity involving the Primary Issue at the time of
          prepayment, Lender shall choose a comparable Treasury Bond, Note or
          Bill (Issue" which Lender reasonably deems to be similar to the
          Primary Issue's characteristics (i.e., rate, remaining time to
          maturity, yield).

          *    At this time there is not a U.S. Treasury Issue for this
               prepayment period. At the time of prepayment, Lender shall select
               in its sole and absolute discretion a U.S. Treasury Issue with
               similar remaining time to maturity as this Note.

     (b)  Calculate the " Value of the Loan. The Present Value of the Loan is
          the, present value of the payments to be made in accordance with this
          Note (all installment payments and any remaining payment due on the
          Maturity Date) discounted at the Reinvestment Yield for the number of
          months remaining from the date of prepayment to the Maturity Date.

     (c)  Subtract the amount of the prepaid proceeds from the Present Value of
          the Loan as of the date of prepayment. Any resulting positive
          differential shall be the premium.

Notwithstanding the above, partial prepayments will be permitted pursuant to the
terms of paragraph 2 of the Property Reserves Agreement, and in the event of a
partial prepayment, the Present Value of the Loan shall be calculated in
accordance with (b) above multiplied by the fraction which results from dividing
the amount of the prepaid proceeds by the principal balance immediately prior to
prepayment. All prepayments shall be made on a regular installment date and
shall be first applied to any payments in inverse order due and not defer the
due date of any payments.

If Borrower has otherwise fully complied with the preceding paragraphs, then,
during the last 90 days prior to the Maturity Date, provided no Event of Default
exists, no Make Whole Premium shall be payable.

3. Borrower agrees that if Lender accelerates the whole or any part of the
principal sum evidenced hereby after the occurrence of an Event of Default, or
applies any proceeds pursuant to the provisions of the Loan Documents, Borrower
waives any right to prepay said principal sum in whole or in part without
premium and agrees to pay, as yield maintenance protection and not as a penalty,
the Make Whole Premium.

Notwithstanding the above, in the event any proceeds from a casualty or Taking
of the Premises are applied to reduce the principal balance hereof, such
reduction shall be made

<PAGE>

without a Make Whole Premium, provided no Event of Default then exists under the
Loan Documents.

4. If any payment of principal, interest, or other Indebtedness is not made when
due, damages will be incurred by Lender, including additional expense in
handling overdue payments, the amount of which is difficult and impractical to
ascertain. Borrower therefor agrees to pay, upon demand, the sum of four cents
($.04) for each one dollar ($1.00) of each said payment which becomes overdue (
Charge" as a reasonable estimate of the amount of said damages, subject,
however, to the limitations contained in paragraph 6 hereof.

Notwithstanding anything hereinabove to the contrary, the Late Charge assessed
on any amount due on the Maturity Date but not then paid, whether or not by
acceleration, shall not be four cents for each one dollar as described above,
but shall instead be a sum equal to the interest which would have accrued on the
principal balance then outstanding from the date the payment is made to the end
of the month in which the Maturity Date occurs. Such Late Charge shall be in
addition to interest otherwise accruing under this Note.

5. If any Event of Default has occurred and is continuing under the Loan
Documents, the entire principal balance of the Loan, interest then accrued, and
Make Whole Premium, and all other Indebtedness whether or not otherwise then
due, shall at the option of Lender, become immediately due and payable without
demand or notice, and whether or not Lender has exercised said option, interest
shall accrue on the entire principal balance, interest then accrued, Make Whole
Premium and any other Indebtedness then due, at a rate equal to the Default Rate
until fully paid.

6. Notwithstanding anything herein or in any of the other Loan Documents to the
contrary, no provision contained herein or therein which purports to obligate
Borrower to pay any amount of interest or any fees, costs or expenses which are
in excess of the maximum permitted by applicable law, shall be effective to the
extent it calls for the payment of any interest or other amount in excess of
such maximum. All agreements between Borrower and Lender, whether now existing
or hereafter arising and whether written or oral, are hereby limited so that in
no contingency, whether by reason of demand for payment or acceleration of the
maturity hereof or otherwise, shall the interest contracted for, charged or
received by Lender exceed the maximum amount permissible under applicable law.
If, from any circumstance whatsoever, interest would otherwise be payable to
Lender in excess of the maximum lawful amount, the interest payable to Lender
shall be reduced to the maximum amount permitted under applicable law; and if
from any circumstance Lender shall ever receive anything of value deemed
interest by applicable law in excess of the maximum lawful amount, an amount
equal to any excessive interest shall, at the option of Lender, be refunded to
Borrower or be applied to the reduction of the principal hereof, without a Make
Whole Premium and not to the payment of interest or, if such excessive interest
exceeds the unpaid balance of principal hereof such excess shall be refunded to
Borrower. This paragraph shall control all agreements between Borrower and
Lender.

7. Borrower and any endorsers or guarantors waive presentment, protest and
demand, notice of protest, demand and dishonor and nonpayment, and agree the
Maturity Date of this Note or any installment may be extended without affecting
any liability hereunder, and further promise to pay all reasonable costs and
expenses, including but

<PAGE>

not limited to, reasonable attorney's fees incurred by Lender in connection with
any default or in any proceeding to interpret andlor enforce any provision of
the Loan Documents. No release of Borrower from liability hereunder shall
release any other maker, endorser or guarantor hereof

8. This Note is secured by the Loan Documents creating among other things legal
and valid encumbrances on and an assignment of all of Borrower's interest in any
Leases of the Premises located in the District of Columbia. Capitalized terms
used herein and not otherwise defined shall have those meanings given to them in
the Loan Documents. In no event shall such documents be construed inconsistently
with the terms of this Note, and in the event of any discrepancy between any
such documents and this Note, the terms hereof shall govern. The proceeds of
this Note are to be used for business, commercial, investment or other similar
purposes, and no portion thereof will be used for any personal, family or
household use. This Note shall be governed by and construed in accordance with
the laws of the State where the Premises is located, without regard to its
conflict of law principles.

9. Notwithstanding any provision to the contrary in this Note or the Loan
Documents and except as otherwise provided for below, the liability of Borrower
under the Loan Documents shall be limited to the interest of Borrower in the
Premises and the Rents. In the event of foreclosure of the liens evidenced by
the Loan Documents, no judgment for any deficiency upon the Indebtedness
evidenced by the Loan Documents shall be sought or obtained by Lender against
Borrower. Nothing herein shall in any manner limit or impair (i) the lien or
enforcement of the Loan Documents pursuant to the terms thereof or (ii) the
obligations of any indemnitor or guarantor, if any.

     Notwithstanding any provision hereinabove to the contrary, Borrower shall
be personally liable to Lender for:

     (a)  any loss or damage to Lender arising from (i) the sale or forfeiture
          of the Premises resulting from Borrower's failure to pay any of the
          taxes, assessments or charges specified in the Loan Documents or (ii)
          Borrower's failure to insure the Premises in compliance with the
          provisions of the Loan Documents, only to the extent that Lender or
          its Agents have not collected funds in an escrow as a reserve for
          payment of taxes and assessments and insurance;

     (b)  any event or circumstance for which Borrower indemnifies Lender under
          the Environmental Indemnity;

     (c)  nonpayment of taxes, assessments, insurance premiums and utilities for
          the Premises and any penalty or late charge associated with nonpayment
          thereof, only

     to the extent that Lender or its Agents have not collected funds in an
     escrow as a reserve for payment of taxes and assessments and insurance;

(d)  material failure to manage, operate, and maintain the Premises in a
     commercially reasonable manner for similar property types in the
     surrounding geographic area;

<PAGE>

(e)  any sums expended by Lender in fulfilling the obligations of Borrower as
     lessor under any Lease of the Premises prior to a sale of the Premises
     pursuant to foreclosure or power of sale, a bona fide sale (permitted by
     the terms of paragraph 2W) of the Mortgage (it being agreed that "Mortgage"
     as used herein shall be construed to mean "mortgage" or "deed of trust" or
     "trust deed" as the context so requires) or consented to in writing by
     Lender) to an unrelated third party or upon conveyance to Lender of the
     Premises by a deed acceptable to Lender in form and content (each of which
     shall be referred to as a "Sale" for purposes of this paragraph) or
     expended by Lender after a Sale of the Premises for obligations of Borrower
     which arose prior to a Sale of the Premises;

     Borrower's personal liability for items specified in (c), (d) and (e) above
     shall be limited to the amount of rents, issues, proceeds and profits from
     the Premises ("Rents and Profits") received by Borrower for the twenty-four
     (24) months preceding an Event of Default and thereafter; but less any such
     Rents and Profits applied to (A) payment of principal, interest and other
     charges when due under the Loan Documents, or (B) payment of expenses for
     the operation, maintenance, taxes, assessments, utility charges and
     insurance of the Premises including sufficient reserves for the same or
     replacements or renewals thereof ("Operation Expense(s)") provided that (x)
     Borrower has furnished Lender with evidence reasonably satisfactory to
     Lender of the Operation Expenses and payment thereof, and (y) any payments
     to parties related to Borrower shall be considered an Operation Expense
     only to the extent that the amount expended for the Operation Expense does
     not exceed the then current market rate for such Operation Expense.

(f)  any rents or other income regardless of type or source of payment or other
     considerations in lieu thereof (including, but not limited to, common area
     maintenance charges, lease termination payments, refunds of any type,
     prepayment of rents, settlements of litigation, or settlements of past due
     rents) from the Premises which Borrower has received or will receive after
     an Event of Default under the Loan Documents which are not applied to (A)
     payment of principal, interest and other charges when due under the Loan
     Documents or (B) payment of Operation Expenses provided that (x) Borrower
     has furnished Lender with evidence reasonably satisfactory to Lender of the
     Operation Expenses and payment thereof, and (y) any payments to parties
     related to Borrower shall be considered an Operation Expense only to the
     extent that the amount expended for the Operation Expense does not exceed
     the then current market rate for such Operation Expense;

     (g)  any security deposits of tenants not otherwise applied in accordance
          with the terms of the Lease(s), together with any interest on such
          security deposits required by law or the leases, not turned over to
          Lender upon conveyance of the Premises to Lender pursuant to
          foreclosure or power of sale or by a deed acceptable to Lender in form
          and content;

<PAGE>

     (h)  misapplication or misappropriation of tax reserve accounts, tenant
          improvement reserve accounts, security deposits, prepaid rents or
          other similar sums paid to or held by Borrower or any other entity or
          person in connection with the operation of the Premises

     (i)  any insurance or condemnation proceeds or other similar funds or
          payments applied by Borrower in a manner other than as expressly
          provided in the Loan Documents; and

     (j)  any loss or damage to Lender arising from any fraud or willful
          misrepresentation by or on behalf of Borrower, Interest Owner or any
          guarantor regarding the Premises, the making or delivery of any of the
          Loan Documents or in any materials or information provided by or on
          behalf of Borrower, Interest Owner or guarantor, if any, in connection
          with the Loan.

          Notwithstanding anything contained in paragraphs 9(a)(i) and 9(c)
          hereinabove as it relates solely to taxes, assessments and insurance
          premiums, to the extent Lender is impounding for taxes, assessments
          and insurance premiums in accordance with the Loan Documents and
          Borrower has fully complied with all terms and conditions of the Loan
          Documents relating to impounding for the same, then Borrower shall not
          be personally liable for Lender's failure to apply any of said impound
          amounts held by Lender in accordance with the Loan Documents.

     Notwithstanding anything to the contrary in the Loan Documents, the
limitation on liability contained in the first paragraph of this paragraph 9
SHALL BECOME NULL AND VOID and shall be of no further force and effect in the
event:

     (w)  of any breach or violation of paragraph 2(1) (due on sale or
          encumbrance) of the Mortgage, other than (i) the filing of a
          nonmaterial mechanic's lien affecting the Premises or a mechanic's
          lien affecting the Premises for which Borrower has complied with the
          provisions of paragraph 1(e) of the Mortgage, or (ii) the granting of
          any utility or other nonmaterial easement or servitude burdening the
          Premises, or (iii) any transfer or encumbrance of a nonmaterial
          economic interest in the Premises not otherwise set forth in (i) or
          (ii);

     (x)  of any filing by Borrower of a petition in bankruptcy or insolvency or
          a petition or answer seeking any reorganization, arrangement,
          composition, readjustment,


                                       -7-

          liquidation, dissolution or similar relief under the Bankruptcy laws
          of the United States or under any other applicable federal, state or
          other statute or law.

10. If more than one, all obligations and agreements of Borrower are joint and
several.

<PAGE>

Notwithstanding any term or provision contained herein to the contrary, no
personal liability shall under any circumstances be assumed by nor shall at any
time any liability be asserted or enforceable against any manager or member of
the undersigned (nor of the directors, agents, employees, officers,
shareholders, members, partners or principals of such partners), on account of
the Loan or any of the Loan Documents or on account of any of the
above-referenced carve- outs or on account of any warranty, indemnity,
representation, covenant, undertaking or agreement of the undersigned or any
other party therein contained, either express or implied, including, without
limitation, for the payment of any of the principal, interest, late charges,
fees or other charges or other amounts due in connection with the Loan or the
Loan Documents or for any deficiency judgment which the holder hereof may obtain
afler foreclosure under the mortgage, all such personal liability, if any, being
herein expressly waived and released.

11. This Note may not be changed or terminated orally, but only by an agreement
in writing and signed by the party against whom enforcement of any waiver,
change, modification or discharge is sought. All of the rights, privileges and
obligations hereunder shall inure to the benefit of the heirs, successors and
assigns of Lender and shall bind the heirs and permitted successors and assigns
of Borrower.

12. If any provision of this Note shall, for any reason, be held to be invalid
or unenforceable, such invalidity or unenforceability shall not affect any other
provision hereof, but this Note shall be construed as if such invalid or
unenforceable provision had never been contained herein.

13. This Note may be executed in counterparts, each of which shall be deemed an
original; and such counterparts when taken together shall constitute but one
agreement.

                            (Signatures on next page)


                                       -8-

     IN WITNESS WHEREOF, Borrower has caused this Note to be duly executed and
delivered as of the date first set forth above.

1025 VERMONT INVESTORS, L.L.C., a
Delaware limited liability company

By: VERMONT AVENUE MANAGING ASSOCIATES, L.L.C., a Delaware limited liability
company


By: /s/ Andrew J. Czekaj
    ---------------------------------
Name: Andrew J. Czekaj
Title: Manager