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                                                                    Exhibit 4.21


                                 PROMISSORY NOTE

<TABLE>
<CAPTION>
PRINCIPAL       LOAN DATE       MATURITY        LOAN NO       CALL      COLLATERAL      ACCOUNT      OFFICER      INITIALS
---------       ---------       --------        -------       ----      ----------      -------      -------      --------
<S>             <C>             <C>             <C>           <C>       <C>             <C>          <C>          <C>
$87,541.03      09-03-1999      12-31-2001      9100000927                                           121

                      References in the shaded area are for Lender's use only and do not limit the
                             applicability of this document to any particular loan or item.
</TABLE>

BORROWER: PODS, Inc. f/k/a Pods Equity,   LENDER: First National Bank of Florida
          Inc. successor in interest to           1150 Cleveland Street
          Pods, LLC f/k/a Portables on            Clearwater, FL 33755
          Demand Storage, LLC successor,
          in interest by merger, to
          Rope Developments, a Florida
          general partnership
          12200 34th Street
          Clearwater, FL 33762

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<TABLE>
<CAPTION>
<S>                                    <C>                             <C>
PRINCIPAL AMOUNT:  $87,541.03          INTEREST RATE:  7.750%          DATE OF NOTE: SEPTEMBER 3, 1999
</TABLE>

PROMISE TO PAY.  PODS, INC. F/K/A PODS EQUITY, INC. SUCCESSOR IN INTEREST TO
PODS, LLC F/K/A PORTABLES ON DEMAND STORAGE, LLC SUCCESSOR, IN INTEREST BY
MERGER, TO ROPE DEVELOPMENTS, A FLORIDA GENERAL PARTNERSHIP ("BORROWER")
PROMISES TO PAY TO FIRST NATIONAL BANK OF FLORIDA ("LENDER"), OR ORDER, IN
LAWFUL MONEY OF THE UNITED STATES OF AMERICA, THE PRINCIPAL AMOUNT OF EIGHTY
SEVEN THOUSAND FIVE HUNDRED FORTY ONE & 03/100 DOLLARS ($87,541.03), TOGETHER
WITH INTEREST AT THE RATE OF 7.750% PER ANNUM ON THE UNPAID PRINCIPAL BALANCE
FROM SEPTEMBER 3, 1999, UNTIL PAID IN FULL.

PAYMENT.  BORROWER WILL PAY THIS LOAN IN 28 PAYMENTS OF $3,430.12 EACH PAYMENT.
BORROWER'S FIRST PAYMENT IS DUE SEPTEMBER 30, 1999, AND ALL SUBSEQUENT PAYMENTS
ARE DUE ON THE SAME DAY OF EACH MONTHS AFTER THAT. BORROWER'S FINAL PAYMENT WILL
BE DUE ON DECEMBER 31, 2001, AND WILL BE FOR ALL PRINCIPAL AND ALL ACCRUED
INTEREST NOT YET PAID. PAYMENTS INCLUDE PRINCIPAL AND INTEREST. The annual
interest rate for this Note is computed on a 365/360 basis; that is, by applying
the ratio of the annual interest rate over a year of 360 days, multiplied by the
outstanding principal balance, multiplied by the actual number of days the
principal balance is outstanding. Borrower will pay Lender at Lender's address
shown above or at such other place as Lender may designate in writing. Unless
otherwise agreed or required by applicable law, payments will be applied first
to accrued unpaid interest, then to principal, and any remaining amount to any
unpaid collection costs and late charges.

PREPAYMENT; MINIMUM INTEREST CHARGE.  In any event, even upon full payment of
this Note, Borrower understands that Lender is entitled to A MINIMUM INTEREST
CHARGE OF $10.00. Other than Borrower's obligation to pay any minimum interest
charge, Borrower may pay without penalty all or a portion of the amount owed
earlier than it is due. Early payments will not, unless agreed to by Lender in
writing, relieve Borrower of Borrower's obligation to continue to make payments
under the payment schedule. Rather, they will reduce the principal balance due
and may result in Borrower making fewer payments.

LATE CHARGE.  If a payment is 10 DAYS OR MORE LATE, Borrower will be charged
5.000% OF THE UNPAID PORTION OF THE REGULARLY SCHEDULED PAYMENT.

DEFAULT.  Borrower will be in default if any of the following happens: (a)
Borrower fails to make any payment when due. (b) Borrow breaks any promise
Borrower has made to Lender, or Borrower fails to comply with or to perform when
due any other term, obligation, covenant, or condition contained in this Note or
any agreement related to this Note, or in any other agreement or loan Borrower
has with Lender. (c) Borrower defaults under any loan, extension of credit,
security agreement, purchase or sales agreement, or any other agreement, in
favor of any other creditor or person that may materially affect any of
Borrower's property or Borrower's ability to repay this Note or perform
Borrower's obligations under this Note or any of the Related Documents. (d) Any
representation or statement made or furnished to Lender by Borrower or on
Borrower's behalf is false or misleading in any material respect either now or
at the time made or furnished. (e) Borrower becomes insolvent, a receiver is
appointed for any part of Borrower's property, Borrower makes an assignment for
the benefit of creditors, or any proceeding is commenced either by Borrower or
against Borrower under any bankruptcy or insolvency laws. (f) Any creditor tries
to take any of Borrower's property on or in which Lender has a lien or security
interest. This includes a garnishment of any of Borrower's accounts with Lender.
(g) Any guarantor dies or any of the other events described in this default
section occurs with respect to any guarantor of this Note. (h) A material
adverse change occurs in Borrower's financial condition, or Lender believes the
prospect of payment or performance of the Indebtedness is impaired. (i) Failure
to meet the deadlines required by the Year 2000 Compliance Agreement to be Year
Compliant or a reasonable likelihood that Borrower cannot be Year 2000 Compliant
on or before December 31, 1999. (j) LENDER IN GOOD FAITH DEEMS ITSELF INSECURE.

LENDER'S RIGHTS.  Upon default, Lender may declare the entire unpaid principal
balance on this Note and all accrued unpaid interest immediately due, without
notice, and then Borrower will pay that amount. Upon default, including failure
to pay upon final maturity, Lender, at its option, may also, if permitted under
applicable law, increase the interest rate on this Note to 18.000% per annum, if
and to the extent that the increase does not cause the interest rate to exceed
the maximum rate permitted by applicable law. Lender may hire or pay someone
else to help collect this Note if Borrower does not pay. Borrower also will pay
Lender the amount of these costs and expenses, which includes, subject to any
limits under applicable law, Lender's reasonable attorneys' fees and Lender's
legal expenses whether or not there is a lawsuit, including reasonable
attorneys' fees and legal expenses for bankruptcy proceedings (including efforts
to modify or vacate any automatic stay or injunction), appeals, and any
anticipated post-judgment collection services. If not prohibited by applicable
law, Borrower also will pay any court costs, in additional to all other sums
provided by law. THIS NOTE HAS BEEN DELIVERED TO LENDER AND ACCEPTED BY LENDER
IN THE STATE OF FLORIDA. IF THERE IS A LAWSUIT, BORROWER AGREES UPON LENDER'S
REQUEST TO SUBMIT TO THE JURISDICTION OF THE COURTS OF PINELLAS COUNTY, THE
STATE OF FLORIDA. LENDER AND BORROWER HEREBY WAIVE THE RIGHT TO ANY JURY TRIAL
IN ANY ACTION, PROCEEDING, OR COUNTERCLAIM BROUGHT BY EITHER LENDER OR BORROWER
AGAINST THE OTHER. (INITIAL HERE /s/ PSW) THIS NOTE SHALL BE GOVERNED BY AND
                                 -------
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF FLORIDA.

RIGHT OF SETOFF.  Borrower grants to Lender a contractual security interest in,
and hereby assigns, conveys, delivers, pledges, and transfers to Lender all
Borrower's right, title and interest in and to, Borrower's accounts with Lender
(whether checking, savings, or some other account), including without limitation
all accounts held jointly with someone else and all accounts Borrower may open
in the future, excluding however all IRA and Keogh accounts, and all trust
accounts for which the grant of a security interest would be prohibited by law.
Borrower authorizes Lender, to the extent permitted by applicable law, to charge
or setoff all sums owing on this Note against any and all such accounts.

COLLATERAL.  This Note is secured by Collateral as described in Security
Agreement of even date.

PRIOR NOTE.  This is an assignment/assumption of the Promissory Note dated
November 30, 1998; documentary stamps are affixed hereto.

<PAGE>   2
09-03-1999                         PROMISSORY NOTE                       PAGE 2
                                     (CONTINUED)

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GENERAL PROVISIONS.  If any part of this Note cannot be enforced, this fact will
not affect the rest of the Note. Borrower does not agree or intend to pay, and
Lender not agree or intend to contract for, charge, collect, take, reserve or
receive (collectively referred to herein as "charge or collect"), any amount in
the nature of interest or in the nature of a fee for this loan, which would in
any way or event (including demand, prepayment, or acceleration) cause Lender to
charge or collect more for this loan than the maximum Lender would be permitted
to charge or collect by federal law or the law of the State of Florida (as
applicable). Any such excess interest or unauthorized fee shall, instead of
anything stated to the contrary, be applied first to reduce the principal
balance of this loan, and when the principal has been paid in full, be refunded
to Borrower. Lender may delay or forgo enforcing any its rights or remedies
under this Note without losing them. Borrower and any other person who signs,
guarantees or endorses this Note, to the extent allowed by law, waive
presentment, demand for payment, protest and notice of dishonor. Upon any change
in the terms of this Note, and unless otherwise expressly stated in writing, no
party who signs this Note, whether as maker, guarantor, accommodation maker or
endorser, shall be released from liability. All such parties agree that Lender
may renew or extend (repeatedly and for any length of time) this loan, or
release any party or guarantor or collateral; or impair, fail to realize upon or
perfect Lender's security interest in the collateral; and take any other action
deemed necessary by Lender without the consent of or notice to anyone. All such
parties also agree that Lender may modify this loan without the consent of or
notice to anyone other than the party with whom the modification is made.

PRIOR TO SIGNING THIS NOTE, BORROWER READ AND UNDERSTOOD ALL THE PROVISIONS OF
THIS NOTE. BORROWER AGREES TO THE TERMS OF THE NOTE AND ACKNOWLEDGES RECEIPT OF
A COMPLETED COPY OF THE NOTE.

BORROWER:

PODS, INC. F/K/A PODS EQUITY, INC. SUCCESSOR IN INTEREST TO PODS, LLC F/K/A
PORTABLES ON DEMAND STORAGE, LLC SUCCESSOR, IN INTEREST BY MERGER, TO ROPE
DEVELOPMENTS, A FLORIDA GENERAL PARTNERSHIP

By: /s/ Peter S. Warhurst, President
    --------------------------------
    PETER S. WARHURST, PRESIDENT

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