<PAGE>   1
                                                                   EXHIBIT 10.19

                             STOCK PLEDGE AGREEMENT


     This STOCK PLEDGE AGREEMENT (this "Agreement") is entered into as of
October 20, 2000 by and between BINGHAM FINANCIAL SERVICES CORPORATION, a
Michigan corporation ("Pledgor") and SUN COMMUNITIES OPERATING LIMITED
PARTNERSHIP, a Michigan Limited Partnership ("Secured Party").

                                    RECITALS:

     A. Pledgor is a shareholder of e-Cognita Technologies, Inc. ("e-Cognita").

     B. Pledgor executed and delivered to Sun Communities, Inc. a Term
Promissory Note in the original principal amount of $4,000,000, dated September
30, 1997, which note was assigned and delivered by Sun Communities, Inc. to
Secured Party on December 31, 1997 (the "Term Note").

     C. Pledgor has executed and delivered to Secured Party a Demand Promissory
Note in favor of Secured Party in the original principal amount of $10,000,000,
dated March 30, 1999 (the "First Demand Note").

     D. Pledgor has executed and delivered to Secured Party a Demand Promissory
Note in favor of Secured Party in the original principal amount of $50,000,000
dated December 13, 1999 (the "Second Demand Note").

     E. Pledgor has entered into and may in the future enter into various
agreements with Secured Party, pursuant to which Pledgor may have various
contractual, indemnification, warranty and/or other obligations to Secured Party
(the "Contractual Obligations").

     F. To secure the prompt satisfaction by Pledgor of Pledgor's obligations to
Secured Party under the Term Note, the First Demand Note, the Second Demand
Note, the Contractual Obligations and all other obligations of Pledgor to
Secured Party, Pledgor has agreed to execute and deliver this Agreement to
Secured Party.

     NOW, THEREFORE, in consideration of the foregoing, and the mutual covenants
contained herein, the parties agree as follows:

     1. GRANT OF SECURITY INTEREST. As security for the prompt and complete
payment and performance when due of all liabilities, obligations or indebtedness
owing by Pledgor to Secured Party whether under the Term Note, under the First
Demand Note, the Second Demand Note the Contractual Obligations and/or otherwise
(collectively, the "Obligations"), Pledgor pledges and grants to Secured Party a
continuing security interest in, and lien on, all collectively, of Pledgor's
right, title and interest in and to the common stock and the preferred stock of
e-Cognita (collectively, the "Shares"), together with all certificates, options,
warrants or other distributions or rights issued as an addition to, in
substitution or in exchange for, or on account of, the Shares, and all proceeds
of the foregoing, including, without limitation, any and all dividends, cash,
instruments and other property from time to time received, receivable or
otherwise distributed in respect of, or in exchange for, any of the above
(collectively, the "Pledged Stock").


<PAGE>   2


     2. DELIVERY OF CERTIFICATES. Concurrent with the execution and delivery of
this Agreement, Secured Party has retained possession of the stock certificates
evidencing the Shares (the "Certificates"). The Certificates have been retained
by Secured Party in order to perfect the pledge established hereunder and this
Agreement shall be interpreted so as to cause the pledge of the Shares to be
perfected. Secured Party acknowledges that, for all other purposes, Pledgor is
the lawful and beneficial owner of the Shares. Secured Party shall hold the
Certificates in accordance with the terms and conditions of this Agreement.

     3. FUTURE RECEIPTS. If Pledgor receives or becomes entitled to receive any:

        (a) stock certificate(s) issued in respect of the Pledged Stock,
     including, without limitation, any certificate representing a stock
     dividend or payable in respect of the Pledged Stock or issued in connection
     with any increase or reduction of capital, reclassification, merger,
     consolidation, sale of assets, combination of shares, stock split, spin-off
     or split-off;

        (b) option, warrant or right, whether issued as an addition to, in
     substitution or in exchange for, or on account of, any of the Pledged
     Stock; or

        (c) dividends or distributions on the Pledged Stock payable other than
     in cash, including securities issued by other than Secured Party or the
     Company;

Pledgor shall accept the same as Secured Party's agent, in trust for Secured
Party, and shall deliver same to Secured Party, in the exact form received with,
as applicable, Pledgor's endorsement when necessary or appropriate stock powers
duly executed in blank. Any property received by Secured Party hereunder shall
be held by Secured Party pursuant to the terms of this Agreement as additional
security for the Obligations.

     4. CASH DIVIDENDS AND DISTRIBUTIONS. So long as no Event of Default
(defined below) has occurred and is continuing, Pledgor may receive for his own
use all cash dividends and distributions on the Pledged Stock.

     5. VOTING AND OTHER RIGHTS. So long as no Event of Default has occurred and
is continuing, Pledgor may exercise any and all voting and other consensual
rights with respect to the Pledged Stock for any purpose not inconsistent with
the terms of this Agreement.

     6. SECURED PARTY'S DUTIES. Subject to Section 9-207 of the Michigan Uniform
Commercial Code, Secured Party shall have no duty with respect to the Pledged
Stock beyond the exercise of reasonable care to assume the safe custody of the
Pledged Stock while held hereunder. Without limiting the generality of the
foregoing, Secured Party shall have no obligation to take any steps to preserve
rights in the Pledged Stock against any other parties or to exercise any rights
represented thereby; provided, however, that Secured Party may, at its option,
do so and Pledgor shall reimburse the Secured Party for all expenses incurred in
connection therewith.

     7. COVENANTS AND WARRANTS OF PLEDGOR. Pledgor covenants that, until the
Obligations have been satisfied in full, Pledgor will not sell, convey or
otherwise dispose of any of the Pledged Stock or any interest therein, or
create, incur, or permit to exist any pledge, mortgage, lien, charge,
encumbrance or any security interest whatsoever in or with respect to any of the
Pledged Stock except for that created hereby. Pledgor warrants, and will at the
Pledgor's expense defend, the Secured Party's right, title and security interest
in and to the Pledged Stock against the claims of any person.

     8. EVENT OF DEFAULT AND REMEDIES. Upon the occurrence of any violation or
breach


                                      -2-
<PAGE>   3


by Pledgor of the terms and conditions of the Note or this Agreement (an "Event
of Default"), the Secured Party (within its discretion) shall have the right to
exercise each and all of the following remedies (which remedies are cumulative
and are in addition to, and not exclusive of, any rights or remedies provided by
law, including, without limitation, the rights and remedies of a secured party
under the Michigan Uniform Commercial Code):

        (a) CASH DIVIDENDS. All cash dividends and distributions on the Pledged
        Stock shall be paid to the Secured Party. In the event Pledgor shall
        receive any such cash dividends or distributions, Pledgor shall hold
        same as Secured Party's agent, in trust for Secured Party, and shall
        deliver same to Secured Party in the exact form received with the
        Pledgor's endorsement when necessary.

        (b) VOTING RIGHTS. Secured Party, at its option, may vote the Pledged
        Stock in its discretion. Pledgor hereby grants to Secured Party or its
        nominee an irrevocable proxy to exercise all voting and other rights and
        privileges relating to the Pledged Stock, which proxy shall be effective
        immediately upon the occurrence of an Event of Default and written
        notice to Pledgor of Secured Party's election to exercise such proxy,
        and shall be coupled with an interest. After the occurrence of an Event
        of Default and upon request of Secured Party, Pledgor agrees to deliver
        to Secured Party such further evidence of such irrevocable proxy to vote
        the Pledged Stock as Secured Party may request. Any or all of the Pledge
        Stock held by Secured Party hereunder may at any time be registered in
        the name of Secured Party or its nominee, and upon Secured Party's
        request, Pledgor will cause the issuer of the Pledged Stock to effect
        such registration. Pledgor hereby appoints Secured Party as his
        attorney-in-fact to arrange for the transfer of the Pledged Stock to the
        name of Secured Party or its nominee and all acts of Secured Party as
        attorney-in-fact are hereby ratified and confirmed and such power is
        coupled with an interest and is irrevocable until the Obligations are
        paid in full. Secured Party may exercise all rights and privileges
        herein granted with respect to the Pledged Stock without liability and
        Secured Party shall have no duty to exercise any of the aforesaid rights
        or privileges and shall not be responsible for any failure to do so or
        delay in so doing.

        (c) DISPOSITION OF PLEDGED STOCK. Secured Party may, without demand of
        performance or other demand, advertisement or notice of any kind (except
        the notice specified below of time and place of public or private sale)
        to or upon Pledgor or any other person (all of which are, to the extent
        permitted by law, hereby expressly waived), realize upon the Pledged
        Stock or any part thereof, and may sell or otherwise dispose of and
        deliver the Pledged Stock or any part thereof or interest therein, in
        one or more parcels at public or private sale or sales, at any exchange,
        broker's board or at the Secured Party's offices or elsewhere, at such
        prices and on such terms (including, without limitation, a requirement
        that any purchaser purchase the Pledged Stock for investment and without
        any intention to make a distribution thereof) as they may deem best, for
        cash or on credit, or for future delivery without assumption of any
        credit risk, with the right to Secured Party or any purchaser to
        purchase upon any such sale the whole or any part of the Pledged Stock
        free of any right or equity of redemption in Pledgor, which right or
        equity is hereby expressly waived and released. Secured Party need not
        give more than five (5) days notice of the time and place of any public
        sale or of the time after which a private sale may take place, which
        notice Pledgor hereby deems reasonable.

        (d) APPLICATION OF PROCEEDS. Any cash dividend or distribution received
        by Secured Party and the proceeds of any disposition of the Pledged
        Stock by


                                      -3-
<PAGE>   4


        Secured Party shall be applied as follows:

                    (i) First, to the costs and expenses incurred in connection
              with enforcing this Agreement or incidental thereto or to the care
              or safekeeping of any of the Pledged Stock or in any way relating
              to the rights of Secured Party, including reasonable attorneys'
              fees and legal expenses;

                    (ii) Second, to the satisfaction of the Obligations;

                    (iii) Third, to the payment of any other amounts required by
              applicable law (including, without limitation, the Michigan
              Uniform Commercial Code); and

                    (iv) Fourth, to Pledgor to the extent of any surplus
              proceeds.

     9. FURTHER ASSURANCES. Pledgor shall, at any time and from time to time,
upon the written request of Secured Party, execute and deliver such further
documents and do such further acts and things as Secured Party may reasonably
request to effect the purposes of this Agreement.

     10. TERMINATION. Upon the satisfaction in full of the Obligations and the
payment of all additional costs and expenses of Secured Party hereunder, this
Agreement shall terminate and Secured Party shall deliver, or cause to be
delivered, to Pledgor the Certificates necessary to transfer title to the Shares
to Pledgor.

     11. WITHHOLDING TAXES. Pledgor shall pay all withholding taxes on the
Shares, and Pledgor hereby indemnifies Secured Party and its officers,
directors, agents and representatives from and against any and all liability
associated with the withholding taxes on the Shares.

     12. MISCELLANEOUS PROVISIONS.

        (a) This Agreement shall be governed by, and construed and enforced in
accordance with, the laws of the State of Michigan.

        (b) All of the terms contained herein shall survive the consummation of
the transactions contemplated herein, and shall be binding upon and inure to the
benefit of and be enforceable by and against, the parties and their respective
successors, assigns, heirs at law, legal representatives and estates.

        (c) This Agreement and any other documents executed in connection
herewith together constitute the full and entire understanding and agreement
among the parties with respect to the transactions herein contemplated, and
shall supersede all prior understandings or agreements relating thereto, whether
written or oral, all of which are declared to be null and void and of no further
force or effect.

        (d) This Agreement may only be amended or modified, and any of the
terms, conditions, covenants, representations or warranties contained herein may
only be waived, by a written instrument duly executed by the parties.

        (e) The paragraph headings in this Agreement are for convenience of
reference only and are not to be considered in construing this Agreement. This
Agreement may be executed in counterparts and all counterparts, when taken
together, shall constitute but one and the same agreement.



                                      -4-
<PAGE>   5


     IN WITNESS WHEREOF, the parties have executed this Stock Pledge Agreement
as of the day and year above written.


                                  PLEDGOR:

                                  BINGHAM FINANCIAL SERVICES
                                  CORPORATION, a Michigan corporation


                                  By: /s/ Ronald A. Klein
                                     -------------------------------------------

                                  Its: President and Chief Executive Officer
                                      ------------------------------------------


                                  SECURED PARTY:

                                  SUN COMMUNITIES OPERATING LIMITED
                                  PARTNERSHIP,  A MICHIGAN LIMITED
                                  PARTNERSHIP


                                  By:   Sun Communities, Inc., a Maryland
                                        corporation

                                  Its:  General Partner


                                  By:   /s/ Gary  A. Shiffman
                                     -------------------------------------------

                                  Its: President and Chief Executive Officer
                                      ------------------------------------------



                                      -5-