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                                                                   EXHIBIT 10.20

                             SUPPLEMENT TO INDENTURE
                  CONTRACT-BACKED NOTES, CLASS B, SERIES 2001-4

        This SUPPLEMENT TO INDENTURE, dated as of September 1, 2001 (this
"Supplement"), is among MFI Finance Corp. I, a Massachusetts corporation, as
Issuer (the "Issuer"), MicroFinancial Incorporated, a Massachusetts corporation,
as Servicer (the "Servicer") and Wells Fargo Bank Minnesota, National
Association, a national banking association, as Indenture Trustee (in such
capacity, the "Indenture Trustee") and as Back-up Servicer (in such capacity,
the "Back-up Servicer").

        This Supplement incorporates by reference all of the provisions
(including all defined terms) of the Amended and Restated Indenture, dated as of
September 1, 2001 (the "Basic Indenture"), among the Issuer, the Servicer, the
Indenture Trustee and the Back-up Servicer. Reference is further made to (i) the
Servicing Agreement, dated as of March 1, 2000 (as amended by the First
Amendment to Servicing Agreement, dated as of September 1, 2001, the "Servicing
Agreement"), among the Servicer, the Issuer, the Indenture Trustee and the
Back-up Servicer, and (ii) the Contract Acquisition Agreement, dated as of March
1, 2000 (the "Contract Acquisition Agreement"), between the Issuer and Leasecomm
Corporation, as the originator (the "Company").

        The Issuer has duly authorized the execution and delivery of this
Supplement to provide for the issuance of the Issuer's 8.16% Contract-Backed
Notes, Class B, Series 2001-4 (the "Series 2001-4 Notes"), in a maximum
aggregate principal amount of $32,000,000, issuable as provided in the Indenture
and herein. Pursuant to Section 2.02 of the Indenture, this Supplement sets
forth the following additional terms applicable to the Series 2001-4 Notes.

SECTION 1.  SUPPLEMENTAL DEFINITIONS.

        "Accrual Date" means with respect to those Series 2001-4 Notes delivered
on the Delivery Date, September 21, 2001 and with respect to those Series 2001-4
Notes for which the principal amount of such Note is first issued, authenticated
and delivered after the Delivery Date pursuant to Section 3 hereof such later
date as is specified in such Series 2001-4 Note.

        "Class B Note Interest Rate" means, with respect to the Series 2001-4
Notes, 8.16%.

        "Delivery Date" means, with respect to the Series 2001-4 Notes,
September 21, 2001.

        "Initial Payment Date" means with respect to those Series 2001-4 Notes
delivered on the Delivery Date, October 16, 2001 and with respect to those
Series 2001-4 Notes for which the principal amount of such Note is first issued,
authenticated and delivered after the Delivery Date pursuant to Section 3 hereof
such later date as is specified in such Series 2001-4 Note.

        "Interest Calculation Convention" means, with respect to the Series
2001-4 Notes, a 360-day year consisting of twelve months of thirty days each.

        "Note Purchase Agreement" means, with respect to the Series 2001-4
Notes, the Purchase Agreement, dated as of September 21, 2001, between the
Issuer and MFI Finance II, LLC.

        "Placement Agent" means, with respect to the Series 2001-4 Notes,
Rothschild Inc.

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        "Private Placement Memorandum Date" is not applicble with respect to the
Series 2001-4 Notes.

        "Stated Maturity Date" means, with respect to the Series 2001-4 Notes,
February 18, 2008.

        "Transaction Documents Date" means, with respect to any of the
Transaction Documents related to the Series 2001-4 Notes, as of September 1,
2001.

SECTION 2.   REQUIRED PROVISIONS.

        (a)     The Series of Notes to be issued under this Supplement shall be
designated as the Issuer's "Contract-Backed Notes, Class B, Series 2001-4."

        (b)     The maximum aggregate principal amount of Series 2001-4 Notes
that may be issued is $32,000,000.

        (c)     There are no additional Trigger Events applicable to the
Series 2001-4 Notes (other than those specified in any other Supplement in
effect from time to time).

        (d)     Notwithstanding Section 4.02 of the Indenture, no other Series
of Class B notes may be issued while the Series 2001-4 Notes remain Outstanding
without the consent of the Controlling Party and any Rating Agency then rating
any notes secured by the Series 2001-4 Notes.

SECTION 3.   ISSUANCE OF SERIES 2001-4 NOTES IN TWO CLOSINGS.

        If on the Delivery Date the Issuer issues, authenticates and delivers
Series 2001-4 Notes having an aggregate principal amount less than $32,000,000,
the Issuer shall be permitted to issue, authenticate and deliver the remaining
Series 2001-4 Notes in one subsequent closing (the "Second Closing") upon
satisfaction of the following conditions:

        (a)     No default, Event of Default, Trigger Event or Servicer Event of
                Default shall have occurred or be continuing;

        (b)     No Series of Notes issued by the Issuer or MFI Finance II, LLC
                that was rated by a Rating Agency at issuance shall have had its
                credit rating qualified, withdrawn or downgraded;

        (c)     The aggregate principal amount of Series 2001-4 Notes issued,
                authenticated and delivered on the date of the Second Closing
                shall not exceed the lesser of (i) the excess of $32,000,000
                over the principal amount of Series 2001-4 Notes issued,
                authenticated and delivered on the Delivery Date and (ii) the
                excess of the Aggregate IPB as of the most recent Calculation
                Date over the aggregate principal amount of all Class A Notes
                and Class B Notes (of all Series) Outstanding on the date of the
                Second Closing;

        (d)     The Issuer shall have been paid the purchase price specified in
                the Note Purchase Agreement;

        (e)     The Second Closing Date shall occur no later than 90 days after
                the Delivery Date; and

        (f)     The Issuer shall certify in writing to the Indenture Trustee,
                the Controlling Party and the Holders of the Series 2001-4 Notes
                that each of the foregoing conditions has been satisfied.

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SECTION 4.   MISCELLANEOUS.

        (a)     As supplemented by this Supplement, the Indenture is in all
respects ratified and confirmed and the Indenture as so supplemented shall be
read, taken and construed as one and the same instrument. In the event that any
term or provision contained herein shall conflict with or be inconsistent with
any term or provision contained in the Indenture, the terms and conditions of
the Supplement shall be controlling.

        (b)     This Supplement shall be construed in accordance with and
governed by the internal laws of the State of New York applicable to agreements
made and to be performed therein, without regard to the conflict of laws
provisions of any State.

        (c)     This Supplement may be executed in any number of counterparts,
each of which so executed shall be deemed to be an original, but all such
counterparts shall together constitute but one and the same instrument. Delivery
of an executed counterpart of a signature page to this Supplement by telecopier
shall be as effective as delivery of a manually executed counterpart of this
Supplement.

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      IN WITNESS WHEREOF, the Issuer, the Servicer, the Indenture Trustee and
the Back-up Servicer have caused this Supplement to be duly executed by their
respective officers thereunto duly authorized as of the date and year first
above written.

                                            MFI FINANCE CORP. I, as Issuer

                                            By:
                                               ---------------------------
                                                Name:
                                                Title:

                                            MICROFINANCIAL INCORPORATED, as
                                            Servicer

                                            By:
                                               ---------------------------
                                                Name:
                                                Title:

                                            WELLS FARGO BANK MINNESOTA,
                                            NATIONAL ASSOCIATION, as Indenture
                                            Trustee

                                            By:
                                               ---------------------------
                                                Name:
                                                Title:

                                            WELLS FARGO BANK MINNESOTA,
                                            NATIONAL ASSOCIATION, as Back-up
                                            Servicer

                                            By:
                                               ---------------------------
                                                Name:
                                                Title: