<PAGE>
                                                                   Exhibit 10.21
                                 AMENDMENT NO. 1
                                       TO
                              MONITORING AGREEMENT
                              --------------------
                          (EXTENDING MONITORING PERIOD)

         THIS AMENDMENT NO. 1, is made to be effective as of July 1, 2003, and
intended to extend the term for Monitoring Services to be performed under the
Monitoring Agreement ("Agreement") effective as of July 1, 2002, by and between
ProFinance Holdings Corporation, an Ohio Corporation nka ProCentury Corporation
("ProCentury") and Stonehenge Opportunity Fund, LLC, an Ohio limited liability
company ("Stonehenge").

         WHEREAS, ProCentury and Stonehenge wish to extend the term of the
Agreement for the purpose of having Monitoring Services, as defined therein,
continue to be provided;

         NOW THEREFORE, in consideration of the mutual covenants and agreements
contained in the Agreement to be extended hereby, and for other good and
valuable consideration, the adequacy, sufficiency and receipt of which is hereby
acknowledged, ProCentury and Stonehenge agree as follows:

         That paragraph 1. MONITORING SERVICES, as set forth in the Agreement,
be and the same is hereby deleted in its entirety and the following provision is
substituted therefore, as follows:

              1.  MONITORING SERVICES. From July 1, 2003 through the first to
                  occur of either the date the "closing" takes place on
                  ProCentury's initial public offering when the net proceeds
                  therefrom are transferred to ProCentury by the underwriters,
                  or, December 31, 2003 (the "Extended Monitoring Period"),
                  Stonehenge shall perform such Monitoring Services as are
                  reasonably necessary, in Stonehenge's discretion, to monitor
                  its investment in ProFinance, and/or which may be reasonably
                  requested by ProCentury from time to time. Termination
                  pursuant to this provision, if occurring prior to December 31,
                  2003, shall not require prior written notice as contemplated
                  in provision 10. EARLY TERMINATION of the Agreement.

         In all other respects, the provisions of the Agreement shall remain
unchanged and continue to be in full force and effect according to the terms
thereof until the Extended Monitoring Period ends.

         IN WITNESS WHEREOF, the parties hereto have executed this Amendment
No. 1 to the Monitoring Agreement effective as of the date first set forth
above.

<TABLE>
<CAPTION>
         PROCENTURY CORPORATION                     STONEHENGE OPPORTUNITY FUND, LLC

<S>                                             <C>
   By:      /s/ John A. Marazza                 By:    /s/ Michael C.Schuler
         -----------------------------------         ---------------------------------
   Its:     EVP, COO & Secretary                Its:   Principal
         -----------------------------------         ---------------------------------
</TABLE>


<PAGE>


                              MONITORING AGREEMENT
                              --------------------

         THIS AGREEMENT is made to be effective as of July 1, 2002 by and
between ProFinance Holdings Corporation, an Ohio corporation ("ProFinance") and
Stonehenge Opportunity Fund, LLC, an Ohio limited liability company
("Stonehenge").

         WHEREAS, Stonehenge has made a venture capital investment in
ProFinance;

         WHEREAS, Stonehenge expends considerable time and effort in monitoring
its investment in ProFinance, which monitoring activities include but are not
limited to reviewing and evaluating ProFinance's financial statements, attending
meetings with ProFinance management and Board of Directors, and consulting with
ProFinance with respect to ProFinance's business and prospects (collectively,
the "Monitoring Services");

         NOW THEREFORE, in consideration of the mutual covenants and agreements
contained in this Agreement and for good and valuable consideration, the
adequacy, sufficiency and receipt of which is hereby acknowledged, ProFinance
and Stonehenge agree as follows:

         1. MONITORING SERVICES. From July 1, 2002 through June 30, 2003 (the
"Monitoring Period"), Stonehenge shall perform such Monitoring Services as are
reasonably necessary, in Stonehenge's discretion, to monitor its investment in
ProFinance, and/or which may be reasonably requested by ProFinance from time to
time.

         2. MONITORING FEES. In consideration for the Monitoring Services to be
performed by Stonehenge during the Monitoring Period, ProFinance shall pay to
Stonehenge $340,902 in cash (the "Monitoring Fee"), which Monitoring Fee shall
be payable in four (4) quarterly installments as follows: the installment for
the third quarter of 2002 of $86,913 due and payable by December 31, 2002; the
installment for the fourth quarter of 2002 of $86,913 due and payable by March
31, 2003; the installment for the first quarter of 2003 of $85,717 due and
payable by June 30, 2003; and the installment for the second quarter of 2003 or
$84,843.64 due and payable by September 30, 2003.

         3. SEVERABILITY. If any provision of this Agreement is declared or
found to be illegal, unenforceable or void by any administrative agency,
regulatory body or court of competent jurisdiction, such finding shall not
affect the remaining provisions of this Agreement, and all other provisions
hereof shall remain in full force and effect.

         4. GOVERNING LAW. This Agreement and all rights and obligations of the
parties hereunder shall be construed and interpreted under and pursuant to the
laws of the State of Ohio without regard to conflicts of law principles.

         5. WAIVER. No delay or omission by any party hereto to exercise any
right or power arising upon any noncompliance or default by the other party with
respect to any of the terms of this Agreement be construed as a waiver thereof.
A waiver by any of the parties hereto of the fulfillment of any of the
covenants, conditions, or agreements to be performed by the other

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<PAGE>

shall not be construed to be a waiver of any succeeding breach thereof or of any
other covenant, condition or agreement contained herein. No waiver or compromise
of any provision or condition hereof shall be effective unless evidenced by a
written instrument duly executed by the party hereto to be charged with such
waiver or compromise.

         6. ASSIGNMENT. This Agreement shall be binding upon and shall inure to
the benefit of the parties hereto and their respective successors and permitted
assigns. Neither party hereto may assign any of their respective rights and
obligations under this Agreement without the prior written consent of the other.

         7. COUNTERPARTS. This Agreement may be executed in two or more
counterparts, each of which shall be deemed to be an original and all of which
together shall constitute one and the same instrument.

         8. HEADINGS. The headings to the Sections of this Agreement are for
convenience only and in no way define, limit or describe the scope or intent of
this Agreement or any party hereto, nor in any other way affect this Agreement
or any part hereof.

         9. AMENDMENT. This Agreement shall not be altered or amended except
pursuant to an instrument in writing signed by the parties hereto.

         10. EARLY TERMINATION. Either party may terminate this Agreement at any
time during the Monitoring Period upon not less than 30 days prior written
notice of termination to the other party. In the event that this Agreement is
terminated prior to the end of the Monitoring Period, ProFinance shall pay to
Stonehenge any unpaid Monitoring Fees on a prorated basis through the date of
termination, with such payment being due and payable on or before the 120th day
following such termination.

         11. ENTIRE AGREEMENT. This Agreement, including all schedules attached
to this Agreement, constitutes the entire agreement between the parties
pertaining to the subject matter of this Agreement and supersedes all prior or
contemporaneous oral or written agreements, proposals and understandings.

         IN WITNESS WHEREOF, the parties hereto have executed this Agreement to
be effective as of the date first set forth above.

PROFINANCE HOLDINGS CORPORATION               STONEHENGE OPPORTUNITY FUND, LLC

By:     /s/ John A. Marazza                   By:   /s/ Michael C.Schuler
     -------------------------------                ---------------------------
Its:      EVP                                 Its:  Principal
     -------------------------------                ---------------------------


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