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                                                                    EXHIBIT 10.4

THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE UNITED
STATES SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES ACT"). THE HOLDER
HEREOF, BY PURCHASING SUCH SECURITIES AGREES FOR THE BENEFIT OF THE COMPANY THAT
SUCH SECURITIES MAY BE OFFERED, SOLD OR OTHERWISE TRANSFERRED ONLY (A) TO THE
COMPANY, (B) PURSUANT TO AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES
ACT, OR (C) IF REGISTERED UNDER THE SECURITIES ACT AND ANY APPLICABLE STATE
SECURITIES LAWS. ANY UNITED STATES PERSON WHO HOLDS THIS OBLIGATION WILL BE
SUBJECT TO LIMITATIONS UNDER THE UNITED STATES INCOME TAX LAWS, INCLUDING THE
LIMITATIONS PROVIDED IN SECTIONS 165(j) AND 1287(a) OF THE INTERNAL REVENUE CODE
OF 1986, AS AMENDED.

October 1,2002                                                         $168,000

                            6% CONVERTIBLE DEBENTURE

      Metropolitan Health Networks, Inc., a Florida corporation (together with
its successors, the "Company"), for value received hereby promises to pay to:

                                Michael Rosenbaum

(the "Holder") and registered assigns, the principal sum of One Hundred
Sixty-Eight Thousand Dollars ($168,000) or, if less, the principal amount of
this debenture (the "Debenture") then outstanding, on the Maturity Date by wire
transfer of immediately available funds to the Holder in such coin or currency
of the United States of America as at the time of payment shall be legal tender
for the payment of public and private debts, and to pay interest, which shall
begin to accrue on the date of this Debenture, quarterly in arrears, on (i) the
last day of March, June, September and December of each year until the Maturity
Date, commencing December 31, 2002 (unless such day is not a business day, in
which event on the next succeeding business day) (each an "Interest Payment
Date"), (ii) the Maturity Date, (iii) each Conversion Date, as hereafter
defined, and (iv) the date the principal amount of the Debenture shall be
declared to be or shall automatically become due and payable, on the principal
sum hereof outstanding in like coin or currency, at the rates per annum set
forth below, from the most recent Interest Payment Date to which interest has
been paid on this Debenture, or if no interest has been paid on this Debenture,
from the date of this Debenture until payment in full of the principal sum
hereof has been made. The Maturity Date is October 1, 2004.

      The interest rate shall be six percent (6%) per annum (the "Interest
Rate") or, if less, the maximum rate permitted by applicable law. Interest on
this Debenture will be calculated on the basis of a 360-day year of twelve 30
day months. All payments of principal and interest hereunder shall be made for
the benefit of the Holder pursuant to

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the terms of the Agreement (hereafter defined). At the option of the Company,
interest may be paid in cash or in shares of the Company's common stock (the
"Common Stock"), If the Company determines to pay interest in shares of Common
Stock, it shall be required to notify the Holder of such election at least 5
days prior to the Interest Payment Date in question. On each Conversion Date,
interest shall be paid in shares of Common Stock on the portion of the principal
balance of the Debenture then being converted. The number of shares of Common
Stock issued as interest shall be determined by dividing the dollar amount of
interest due on the applicable Interest Payment Date or Conversion Date, as the
case may be, by $0.43.

      This Debenture is issued pursuant to that certain Investment Agreement
dated as of the date hereof between the Company and the Investor named therein
(the "Agreement").

      The Company shall keep a register, attached hereto as Annex A (the
"Register"), in which shall be entered the names and addresses of the registered
holder of this Debenture and particulars of this Debenture held by such holder
and of all transfers of this Debenture. References to the "Holder" or "Holders"
shall mean the Person listed in the Register as registered holder of such
Debenture. The ownership of this Debenture shall be proven by the Register.

      1.    PAYMENT OF PRINCIPAL. All unpaid principal and interest under this
Debenture shall be repaid in full on October 1, 2004 (the "Maturity Date"). The
Company may prepay all of the principal and interest due under this Note on the
terms specified in Section 2.

      2.    PRE-PAYMENT. The Company may, at its option, pre-pay all amounts due
under this Debenture at any time before the Maturity Date by serving Holder with
written notice specifying its intent to so prepay (a "Prepayment Notice") at a
repayment price of 102% of the principal amount then outstanding plus all
accrued but unpaid interest, until the first anniversary of its date of issuance
("First Anniversary Date") and 101% of the principal amount then outstanding
plus all accrued but unpaid interest, from the First Anniversary Date until the
Maturity Date (the "Prepayment Price"). Upon receipt of a Prepayment Notice, the
Holder shall have 7 days to serve the Company with a Notice of Conversion
exercising Holder's conversion rights pursuant to Article 5 hereof. Any Notice
of Conversion so served shall take priority over a prior served Prepayment
Notice.

      3.    RANKING. This Debenture shall rank senior to any indebtedness
created by the Company following the date hereof and pari-passu in respect to
any indebtedness of the Company outstanding as of the date hereof.

      4.    DEFAULT. For purposes of this Debenture, an "Event of Default" shall
mean:

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            (a)   failure by the Company to pay or repay when due, all or any
      part of the principal or interest of the Debenture;

            (b)   the Company or any subsidiary of the Company has commenced a
      voluntary case or other proceeding seeking liquidation, winding-up,
      reorganization or other relief with respect to itself or its debts under
      any bankruptcy, insolvency, moratorium or other similar law now or
      hereafter in effect or seeking the appointment of a trustee, receiver,
      liquidator, custodian or other similar official of it or any substantial
      part of its property, or has consented to any such relief or to the
      appointment of or taking possession by any such official in an involuntary
      case or other proceeding commenced against it, or has made a general
      assignment for the benefit of creditors, or has failed generally to pay
      any of its material debts as they become due, or has taken any corporate
      action to authorize any of the foregoing;

            (c)   an involuntary case or other proceeding has been commenced
      against the Company or any subsidiary of the Company seeking liquidation,
      winding-up, reorganization or other relief with respect to it or its debts
      under any bankruptcy, insolvency, moratorium or other similar law now or
      hereafter in effect or seeking the appointment of a trustee, receiver,
      liquidator, custodian or other similar official of it or any substantial
      part of its property, and such involuntary case or other proceeding shall
      remain undismissed and unstayed for a period of 60 days, or an order for
      relief has been entered against the Company or any subsidiary of the
      Company under the federal bankruptcy laws as now or hereafter in effect;

            (d)   any representation, warranty, certification or statement made
      by the Company in this Debenture or the Agreement shall prove to have been
      untrue in any material respect when made.

In the event of the occurrence of an Event of Default that has not been cured by
the Company within 10 days of the receipt of written notice from Holder of the
Event of Default, (i) all unpaid principal under this note shall immediately
begin to accrue interest at the Interest Rate plus 2% per annum or, if less, the
maximum rate permitted by applicable law ("Default Interest"), and shall
continue to accrue interest at the Default Interest rate until such time as all
Events of Default have been cured, and (ii) the Holder hereof may by notice to
the Company declare this Note to be immediately due and payable.

      5.    CONVERSION.

            5.1   CONVERSION OF DEBENTURE. The Holder shall have the right, at
      its option, at any time from and after the date of issuance of this
      Debenture, to convert the principal amount of this Debenture, or any
      portion of such principal amount, into that number of fully paid and
      nonassessable shares of Common

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      Stock determined pursuant to this Section 5.1. The number of shares of
      Common Stock to be issued upon each conversion of this Debenture shall be
      determined by dividing the Conversion Amount (as defined below) by the
      Conversion Price in effect on the date (the "Conversion Date") a notice of
      conversion is delivered to the Company (a "Notice of Conversion"), as
      applicable, by the Holder by facsimile or other reasonable means of
      communication dispatched prior to 4:00 p.m., E.S.T. The term "Conversion
      Amount" means, with respect to any conversion of this Debenture, the sum
      of (1) the principal amount of this Debenture to be converted in such
      conversion plus (2) accrued and unpaid interest, if any, on such principal
      amount at the interest rates provided in this Debenture to the Conversion
      Date plus (3) Default Interest, if any, on such principal amount.

            5.2   CONVERSION PRICE AND LIMITATION. At the option of the Holder,
      any portion or all of the outstanding principal amount of this Debenture
      shall be converted into a number of shares of Common Stock at the
      conversion price (the "Conversion Price") equal to the lesser of (i) $0.46
      (the "Fixed Conversion Price") and (ii) $0.43 (the "Formula Conversion
      Price").

            5.3   EVENT OF DEFAULT CONVERSION PRICE. Notwithstanding the
      foregoing in Section 5.2, upon the occurrence of an Event of Default (as
      defined above) and for so long as any Debenture remains outstanding the
      Conversion Price shall be equal to the lesser of (i) the Fixed Conversion
      Price and (ii) 75% of the average of the volume weighted average sales
      prices of the Common Stock, as reported on Bloomberg, L.P., for the five
      Trading Days immediately preceding the date of the any Notice of
      Conversion submitted by Holder following an Event of Default.

            5.4 AUTHORIZED SHARES. The Company (i) shall promptly irrevocably
      instruct the Company's transfer agent to issue certificates for the Common
      Stock issuable upon conversion of this Debenture and (ii) agrees that its
      issuance of this Debenture shall constitute full authority to its
      officers and agents who are charged with the duty of executing stock
      certificates to execute and issue the necessary certificates for shares of
      Common Stock in accordance with the terms and conditions of this
      Debenture.

                  (b)   The Company shall not be required to pay any tax which
      may be payable in respect of any transfer involved in the issuance and
      delivery of shares of Common Stock or other securities or property on
      conversion of this Debenture in a name other than that of the Holder (or
      in street name), and the Company shall not be required to issue or deliver
      any such shares or other securities or property unless and until the
      person or persons (other than the Holder or the custodian in whose street
      name such shares are to be held for the Holder's account) requesting the
      issuance thereof shall have paid to the Company the amount of any such tax
      or shall have established to the satisfaction

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      of the Company that such tax has been paid.

                  (c)   Upon receipt by the Company of a Notice of Conversion,
      the Holder shall be deemed to be the holder of record of the Common Stock
      issuable upon such conversion, the outstanding principal amount and the
      amount of accrued and unpaid interest on this Debenture shall be deemed
      reduced to reflect such conversion, and, unless the Company defaults on
      its obligations under this Article 5, all rights with respect to the
      portion of this Debenture being so converted shall forthwith terminate
      except the right to receive the Common Stock or other securities, cash or
      other assets, as herein provided, on such conversion. If the Holder shall
      have given a Notice of Conversion as provided herein, the Company's
      obligation to issue and deliver the certificates for shares of Common
      Stock shall be absolute and unconditional, irrespective of the absence of
      any action by the Holder to enforce the same, any waiver or consent with
      respect to any provisions thereof, the recovery of any judgment against
      any person or any action by the Holder to enforce the same, any failure or
      delay in the enforcement of any other obligation of the Company to the
      Holder of record, or any setoff, counterclaim, recoupment, limitation or
      termination, or any breach or alleged breach by the Holder of any
      obligation to the Company. The date of receipt (including receipt via
      telecopy) of such Notice of Conversion shall be the Conversion Date so
      long as it is received before 4:00 p.m., E.S.T., on such date.

                  (d)   Notwithstanding the foregoing, if a Holder has not
      received certificates for all shares of Common Stock prior to the
      expiration of 10 days from the date of the Notice of Conversion, then
      (unless the Holder otherwise elects to retain its status as a holder of
      Common Stock by so notifying the Company), the Holder shall regain the
      rights of a Holder of this Debenture with respect to such unconverted
      portions of this Debenture and the Company shall, as soon as practicable,
      return such unconverted Debenture to the holder or, if the Debenture has
      not been surrendered, adjust its records to reflect that such portion of
      this Debenture not been converted. In all cases, the Holder shall retain
      all of its rights and remedies.

                  (e)   In lieu of delivering physical certificates representing
      the Common Stock issuable upon conversion, provided the Company's transfer
      agent is participating in the Depository Trust Company ("DTC") Fast
      Automated Securities Transfer program, upon request of the Holder, the
      Company shall use its best efforts to cause its transfer agent to
      electronically transmit the Common Stock issuable upon conversion to the
      Holder by crediting the account of Holder's Prime Broker with DTC through
      its Deposit Withdrawal Agent Commission System.

            5.6   MANDATORY CONVERSION. In the event the volume weighted average
      sales price for the Common Stock, as reported by Bloomberg L.P., is equal
      to or greater than $1.50 for 60 consecutive Trading Days at any time

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      following the date of this Debenture, Holder shall be required to convert
      this Debenture at the then applicable Conversion Price; provided, however,
      this provision shall be void if at the time Holder is required to convert
      this Debenture, the Registration Statement (as defined in Section 6) is
      not effective with the Commission.

      6.    REGISTRATION RIGHTS. The Company shall prepare and file a
registration statement (the "Registration Statement") covering the resale of the
shares of Common Stock issuable upon the conversion of this Debenture on or
before the date that is one year after the date of this Debenture. Upon filing,
the Company shall use its reasonable best efforts to cause the Registration
Statement to be declared effective by the Commission as soon after filing as is
reasonably possible.

            In addition to the foregoing, Holder shall have the piggyback
registration rights as set forth in this paragraph. Whenever the Company
proposes to file a Registration Statement for the registration of shares of its
Common Stock, the Company will, prior to such filing, give fifteen (15) days
prior written notice to the Holder of its intention to do so and, upon the
written request of the Holder given within ten (10) days after receipt of such
notice, the Company shall, subject to the terms of this Agreement, use its
reasonable best efforts to cause the shares of Common Stock issuable upon the
conversion of this Debenture to be included in said Registration Statement, and
to be registered under the Securities Act to the extent necessary to permit
their sale.

      7.    MISCELLANEOUS. This Debenture shall be deemed to be a contract made
under the laws of the State of Florida, and for all purposes shall be governed
by and construed in accordance with the laws of said State. The parties hereto,
including all guarantors or endorsers, hereby waive presentment, demand, notice,
protest and all other demands and notices in connection with the delivery,
acceptance, performance and enforcement of this Debenture, except as
specifically provided herein, and asset to extensions of the time of payment, or
forbearance or other indulgence without notice. The Company hereby submits to
the exclusive jurisdiction of the United States District Court for Florida and
of any state court sitting in Palm Beach County, Florida for purposes of all
legal proceedings arising out of or relating to this Debenture. The Company
irrevocably waives, to the fullest extent permitted by law, any objection which
it may now or hereafter have to the laying of the venue of any such proceeding
brought in such a court and any claim that any such proceeding brought in such a
court has been brought in an inconvenient forum. The Company hereby irrevocably
waives any and all right to trial by jury in any legal proceeding arising out of
or relating to this Debenture.

      The Holder of this Debenture by acceptance of this Debenture agrees to be
bound by the provisions of this Debenture which are expressly binding on such
Holder.

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      IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed.

      Dated: OCTOBER 1, 2002
                                       METROPOLITAN HEALTH NETWORKS, INC.

                                       By: /s/ FRED STEINBERG
                                           -----------------------------------
                                       Name: FRED STEINBERG
                                       Title: PRESIDENT/CEO

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