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                                                                    Exhibit 10.1

                                 PROMISSORY NOTE


$3,640,000                                                   As of March 8, 2000

      FOR VALUE RECEIVED, the undersigned, Echelon Residential Holdings LLC, a
Delaware limited liability company with a principal address of 450 Carillon
Parkway, Suite 200, St. Petersburg, FL 33716 (hereinafter "the Maker"), promises
to pay to the order of AIRFUND II International Limited Partnership, with a
principal address of 88 Broad Street, Boston, MA 02110 (together with any other
holder hereof, the "Payee") or at such address or at such other place as the
Payee may from time to time designate in writing, the principal sum of

                THREE MILLION SIX HUNDRED FORTY THOUSAND DOLLARS

($3,640,000), together with interest on the unpaid principal balance hereof from
time to time at a fixed rate equal to fourteen percent (14.0%) per annum through
that date which is twenty-four (24) months from the date hereof and eighteen
percent (18%) per annum thereafter. Such interest shall accrue and compound on a
monthly basis but shall not be due and payable until the Maturity Date. In the
absence of demonstrable error, the books and records of the Payee shall
constitute conclusive evidence of the unpaid principal balance hereof from time
to time.

      This Note may be prepaid, in whole or from time to time in part, at any
time, without premium or penalty. All payments shall be applied first to
collection costs, then to accrued interest and any remainder in payment of
principal. The principal amount prepaid, if any, may not at any time be
reborrowed.

      If not sooner paid, all outstanding principal and accrued and unpaid
interest thereon shall be due and payable on that date which is thirty (30)
months from the date hereof (the "Maturity Date").

      All payments hereunder shall be payable in lawful money of the United
States which shall be legal tender for public and private debts at the time of
payment. Interest shall be calculated on the basis of a year consisting of 360
days and payable for the actual number of days elapsed (including the first day
but excluding the last day), including any time extended by reason of Saturdays,
Sundays and holidays.

      It is expressly agreed that the occurrence of any one or more of the
following shall constitute an "Event of Default" hereunder:

      (a) any failure to pay any amount or installment of interest or principal
and interest whereon the same is payable as above expressed;

      (b) any representation or warranty made by the Maker in connection
herewith be untrue when made or not be fulfilled;
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      (c) failure to observe or perform any other covenant, agreement,
condition, term or provision hereof;

      (d) the Borrower or any guarantor or any member or joint venturer in the
Borrower shall be involved in financial difficulties as evidenced by: (1) its
commencement of a voluntary case under Title 11 of the United States Code as
from time to time in effect, or its authorizing, by appropriate proceedings, the
commencement of such a voluntary case; (2) its filing an answer or other
pleading admitting or failing to deny the material allegations of a petition
filed against it commencing an involuntary case under said Title 11, or seeking,
consenting to or acquiescing in the relief therein provided, or by its failing
to controvert timely the material allegations of any such petition; (3) the
entry of an order for relief in any involuntary case commenced under said Title
11; (4) its seeking relief as a debtor under any applicable law, other than said
Title 11, of any jurisdiction relating to the liquidation or reorganization of
debtors or to the modification or alteration of the rights of creditors, or its
consenting to or acquiescing in such relief; (5) the entry of an order by a
court of competent jurisdiction (i) finding it to be bankrupt or insolvent, (ii)
ordering or approving its liquidation, reorganization or any modification or
alteration of the rights of creditors, or (iii) assuming custody of, or
appointing a receiver or other custodian for, all or a substantial part of its
property; or (6) its making an assignment for the benefit of, or entering into a
composition with, its creditors, or appointing or consenting to the appointment
of a receiver or other custodian for all or a substantial part of its property.

      If any such Event of Default hereunder shall occur, the Payee may declare
to be immediately due and payable the then outstanding principal balance under
this Note, together with all accrued and unpaid interest thereon, and all other
amounts payable to the Payee hereunder, whereupon all such amounts shall become
and be due and payable immediately. The failure of the Payee to exercise said
option to accelerate shall not constitute a waiver of the right to exercise the
same at any other time.

      The Maker will pay on demand all costs and expenses, including reasonable
attorneys' fees, incurred or paid by the Payee in enforcing or collecting any of
the obligations of the Maker hereunder. The Maker agrees that all such costs and
expenses and all other expenditures by the Payees on account hereof which are
not reimbursed by the Maker immediately upon demand, and all amounts due under
this Note after maturity and any amounts due hereunder if an Event of Default
shall occur hereunder shall bear interest at a rate equal to the lesser of
eighteen percent (18.0%) per annum or the maximum rate permitted by law until
such expenditures are repaid or this Note and such amounts are paid in full to
the Payee.

      Notwithstanding any other provision hereof, the Maker shall not be
required to pay any amount pursuant hereto which is in excess of the maximum
amount permitted under applicable law. It is the intention of the parties hereto
to conform strictly to any applicable usury law, and it is agreed that if any
amount contracted for, chargeable or receivable under this Note shall exceed the
maximum amount permitted under any such law, any such excess shall be deemed a
mistake and cancelled automatically and, if theretofore paid, shall be refunded
to the Maker or, at the Payee's sole option, shall be applied as set forth
above.
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      All notices required or permitted to be given hereunder shall be given in
the writing and shall be effective when mailed, postage prepaid, by registered
or certified mail, addressed in the case of the Maker to it at the address of
the Maker set forth above and in the case of the Payee to it at the address of
the Payee set forth above or to such other address as either the Maker or the
Payee may from time to time specify by like notice.

      All of the provisions of this Note shall be binding upon and inure to the
benefit of the Maker and the Payee and their respective successors and assigns.
This Note shall be governed by and construed in accordance with the internal
laws of The Commonwealth of Massachusetts.

      The Maker and every indorser and guarantor hereof hereby consents to any
extension of time of payment hereof, release of all or any part of the security
for the payment hereof, or release of any party liable for this obligation, and
waives presentment for payment, demand, protest and notice of dishonor. Any such
extension or release may be made without notice to the Maker and without
discharging their liability.

      IN WITNESS WHEREOF, the Maker has executed and delivered this Note, under
seal, on the day and year first written above.

                                    ECHELON RESIDENTIAL HOLDINGS LLC


                                    /s/ James A. Coyne
                                    -----------------------
                                    James A. Coyne, Manager