Document:

<PAGE>   1
EXHIBIT 4.2

                           NATIONAL AUTO CREDIT, INC.
    AUTHORIZED CAPITAL STOCK: 40,000,000 Shares Common Stock, par value $.05;
                2,000,000 Shares Preferred Stock, par value $.50

            OF SERIES C PREFERRED STOCK OF NATIONAL AUTO CREDIT, INC.

The Series C Preferred Stock has a par value of $.50 per share. The Series C
Preferred Stock does not have voting rights. The Series C Preferred Stock is
subject to forfeiture and return to the issuer in accordance with the terms set
forth in a certain Merger Agreement dated December 15, 2000, entered into
between National Auto Credit, Inc., Zoomlot Corporation and former shareholders
of Zoomlot Corporation ("Merger Agreement"). No dividend shall be paid upon the
Common Stock unless an amount equal to ten times such dividend shall be first
paid to each share of Series B and Series C Preferred Stock. The Series C
Preferred Stock has no other rights to dividends except as may otherwise be
required by state law. In the event of liquidation, dissolution or winding up of
the issuer, voluntary or involuntary, the Series C Preferred Stock will be
entitled to receive an amount per share equal to ten times any amount payable to
the Common Stock upon any such liquidation or dissolution.

At any time after the earlier of September 30, 2003 or the occurrence of a
"Redemption Event," as defined in the Merger Agreement, but in any event, no
earlier than January 1, 2003, the holder of a share of Series C Preferred Stock
will be entitled to redeem each such share for a cash payment by the issuer
equal to the greater of: (a) $15.00 (as adjusted for any stock splits, stock
dividends, recapitalizations or the like) plus all declared but unpaid dividends
on such shares or (b) ten (10) times the fair market price of a share of Common
Stock as of the date notice of redemption is received by the Company. Any shares
of Series C Preferred Stock, however, that are subject to the forfeiture may not
be redeemed until such forfeiture provisions no longer apply. The issuer also
has certain rights at any time after January 4, 2001, to redeem all or any
portion of the outstanding shares of Series C Preferred Stock by paying to the
holder of such shares being redeemed an amount equal to the product of (A) the
number of shares of Series C Preferred Stock being redeemed times (B) the
greater of (x) $15.00 (as adjusted for any stock splits, stock dividends,
recapitalizations or the like) plus all declared but unpaid dividends on such
shares or (y) ten (10) times the Fair Market Value of a share of Common Stock as
of the date the notice of redemption was given to the holder of shares of Series
C Preferred Stock. To the extent any holder should possess non-forfeitable
shares of Series C Preferred Stock at the time the Company gives any notice of
redemption, such shares of non-forfeitable Series C Preferred Stock shall be
surrendered to the Company, prior to the surrender of forfeitable Series C
Preferred Stock.

WITNESS THE FACSIMILE SEAL OF THE CORPORATION AND THE FACSIMILE SIGNATURES OF
ITS DULY AUTHORIZED OFFICERS.

-----------------------------              ------------------------------
SECRETARY                                  PRESIDENT<PAGE>

                                                                   EXHIBIT 10.31

                         AGREEMENT FOR PURCHASE AND SALE

         This Agreement for Purchase and Sale (the "Agreement"), is made and
entered as of February 9, 2001, by and among Black Warrior Wireline Corp., a
Delaware corporation ("Seller"), and Charles E. Underbrink (the "Purchaser") and
sets forth the terms and conditions of the sale and purchase of warrants to
purchase shares of Seller's common stock par value $0.005 per share (the "Common
Stock"), for 700,000 shares, being issued as of the date hereof and
substantially in the form attached hereto as Exhibit A (the "Warrants").

         WHEREAS, Seller has requested Purchaser to provide a $5,000,000
principal and interest payment guaranty to Seller's senior lender (Coast
Business Credit) in connection with securing financing from such lender, and
Purchaser has agreed to provide such guaranty, as evidenced by the Principal and
Interest Payment Guaranty dated as of January 24, 2000 between Coast Business
Credit, Purchaser and others.

         WHEREAS, Seller desires to issue to Purchaser the Warrants, which
Warrants shall be delivered to Purchaser at the time this document is executed.

         WHEREAS, Seller desires to grant to Purchaser certain registration
rights in respect of the Common Stock that may be acquired on the exercise of
the Warrants, which registration rights shall have the terms and be subject to
the conditions set forth in the Registration Rights Agreement dated as of the
date hereof between Seller and Purchaser as amended and modified and
substantially in the form attached hereto as Exhibit B (the "Registration Rights
Agreement").

         WHEREAS, this Agreement, the Warrants, and the Registration Rights
Agreement are collectively referred to herein as the "Transaction Documents."

         NOW, THEREFORE, in consideration of the premises and the
representations, warranties and agreements herein, the parties agree as follows:

                                    ARTICLE I
                                PURCHASE AND SALE

         1.1 Purchase and Sale of the Warrants. Subject to the terms of this
Agreement, Seller agrees to and does hereby issue, sell and deliver the Warrants
to Purchaser at the Closing (as defined herein), and Purchaser agrees to and
does hereby purchase and accept the Warrants from Seller.

         1.2 Consideration for Purchase of the Warrants. As consideration for
the purchase of each of the Warrants issued and to be issued hereunder (the
"Consideration"), subject to the terms of this Agreement, Purchaser hereby
agrees provide a $5,000,000 principal and interest payment guaranty to Coast
Business Credit.

<PAGE>

                                   ARTICLE II
                    REPRESENTATIONS AND WARRANTIES OF SELLER

         Seller represents and warrants to Purchaser that each of the following
statements (i) are true and correct on the date hereof:

         2.1 Authority. Subject to Section 3.1 hereof, Seller has all requisite
corporate power and authority to enter into the Transaction Documents and to
consummate the transactions contemplated thereby. The execution and delivery of
the Transaction Documents and the consummation of the transactions contemplated
thereby have been duly authorized by all necessary corporate action on the part
of Seller. Subject to Section 3.1 hereof, the Transaction Documents have been
executed and delivered by Seller and constitute the valid and binding obligation
of Seller, enforceable in accordance with their terms, subject to bankruptcy,
insolvency, moratorium and other similar laws affecting creditors' rights
generally and general principles of equity (regardless of whether such
enforceability is considered in a proceeding in equity or at law).

         2.2 Approvals. Subject to Section 3.1 hereof, there is no legal
impediment to the execution and delivery of the Transaction Documents by Seller
or to the consummation of the transactions contemplated thereby, and no filing
or registration with, or authorization, consent or approval of, a Governmental
Entity, shareholders or any other third party is necessary for the consummation
by Seller of the transactions contemplated thereby.

         2.3 Capitalization. Subject to Section 3.1 hereof, all of the Common
Stock issued on the exercise of the Warrants will be fully paid, non-assessable
and free and clear of any Encumbrances. As used in this Agreement, the term
"Encumbrance" means and includes (i) any security interest, mortgage, deed of
trust, lien, charge, pledge, proxy, adverse claim, equity, power of attorney, or
restriction of any kind, including but not limited to, any restriction or
servitude on the use, transfer, receipt of income, or other exercise of any
attributes of ownership, and (ii) any Uniform Commercial Code financing
statement or other public filing, notice or record that by its terms purports to
evidence or notify interested parties of any of the matters referred to in
clause (i) that has not been terminated or released by another proper public
filing, notice or record.

         2.4 Disclosures. Neither this Agreement nor any Exhibit or Schedule
hereto, nor any certificate or other instrument furnished to Purchaser or
Purchaser or its counsel by Seller in connection with the transactions
contemplated hereby, contains any untrue statement of a material fact or omits
to state a material fact necessary in order to make the statements contained
herein or therein, in the light of the circumstances under which they were made,
not misleading.

<PAGE>

                                   ARTICLE III
                                    COVENANTS

         3.1 Capitalization. Seller agrees that, on or before February 28, 2001,
the Seller shall secure an amendment to Seller's Articles or Certificate of
Incorporation to increase the number of shares that the Seller is authorized to
issue to a number sufficient to authorize the issuance of the current
outstanding shares of the Seller and all shares that are issuable upon the
conversion of all of the Seller's convertible notes and securities and upon the
exercise of any warrants or options to purchase the Seller's Common Stock.

                                   ARTICLE IV
                                   THE CLOSING

         4.1 Time and Place. The closing of the purchase and sale of the
Warrants (the "Closing") will take place as of a date agreed to by the parties
(the "Closing Date"), at the offices of Rosen, Cook & Sledge unless another time
and place are agreed to by the parties.

         4.2 Documents to be Delivered at Closing. The Seller shall deliver, or
cause to be delivered, to Purchaser at the Closing the following documents:

             4.2.1   this Agreement;

             4.2.2   Warrants to purchase up to an aggregate of 700,000 shares
of Common Stock;

             4.2.3   the Registration Rights Agreement;

                                    ARTICLE V
                               GENERAL PROVISIONS

         5.1 Survival of Representations, Warranties and Agreements. The
representations, warranties and agreements contained in this Agreement shall
survive the Closing.

         5.2 Notices. All notices or other communications which are required or
may be given under this Agreement shall be in writing and shall be deemed to
have been duly given when delivered in person, transmitted by telecopier (with
receipt confirmed) or mailed by registered or certified first class mail,
postage prepaid, return receipt requested to the parties hereto at the address
set forth below (as the same may be changed from time to time by notice
similarly given) or the last known business or residence address of such other
person as may be designated by either party hereto in writing.

             (a)     If to Seller:       Black Warrior Wireline Corp.
                                         3748 Highway #45 North
                                         Columbus, Mississippi  39701
                                         Attn:  William L. Jenkins

<PAGE>

             (b)     If to Purchaser:    Charles E. Underbrink
                                         7114 Lansing Island Drive
                                         Indian Harbour Beach, FL 32937

         5.3 Miscellaneous. This Agreement (i) constitutes the entire agreement
and supersedes all other prior agreements and understandings, both written and
oral, among the parties, or any of them, with respect to the subject matter
hereof, (ii) shall be binding upon and inure to the benefit of the parties
hereto and their respective successors and assigns and is not intended to confer
upon any other person any rights or remedies hereunder, (iii) shall be governed
in all respects, including validity, interpretation and effect, by the laws of
the State of Delaware, and (iv) may be executed in two or more counterparts
which together shall constitute a single agreement.

         5.4 Assignment.

             (a) Neither this Agreement nor any of the rights, interests or
obligations hereunder shall be assigned by Seller (whether by operation of law
or otherwise) without the prior written consent of the Purchaser.

             (b) Purchaser may assign its rights and obligations hereunder,
under the Warrants or any other Transaction Document, subject to the terms
hereof and upon prior written notice to Seller. Each such assignee (an
"Assignee") shall execute an Assignment and Acceptance substantially in the form
of Exhibit C. Upon the execution of such Assignment and Acceptance by such
Assignee, (i) the Assignee shall be a "Purchaser" hereunder and, to the extent
provided in the Assignment and Acceptance, shall have the rights and obligations
of a Purchaser hereunder, and (ii) the assigning Purchaser (an "Assignor")
shall, to the extent provided in the Assignment and Acceptance, be released from
its obligations hereunder.

             (c) An Assignor hereunder shall, if requested by the Assignee,
deliver the Warrants in favor of such Assignor to the Seller, and the Seller
shall issue replacement Warrants in favor of the Assignor and the Assignee in
the amounts and for such shares as are indicated in the Assignment and
Acceptance. The replacement Warrants shall be issued for an exercise price per
share equal to the exercise price set forth in the Warrants to be delivered to
Seller under this Section 5.4(c).

         5.5 Counterparts. This Agreement may be executed in one or more
counterparts, each of which constitutes an original execution and, in the
aggregate, constitute a single document.

         5.6 Expense Reimbursement. Seller will reimburse Purchaser all of
Purchaser's direct costs relating to the negotiation, documentation and closing
of the transactions contemplated by this Agreement, including without limitation
the direct fees and expenses of counsel for Purchaser.

         5.7 Restrictions on Transfer. Purchaser shall not transfer the Warrants
or any new warrants described in Section 1.4 of this Agreement, except as
provided in the Warrants and provided further that the Warrants may be
distributed to the partners of the Purchaser.

<PAGE>

                             SELLER'S SIGNATURE PAGE

         IN WITNESS WHEREOF, Seller has signed this Agreement as of the date
first written above.

                                              BLACK WARRIOR WIRELINE CORP.

                                              By:
                                                 -------------------------------
                                                   William L. Jenkins, President

<PAGE>

                           PURCHASER'S SIGNATURE PAGE

         IN WITNESS WHEREOF, Purchaser has signed this Agreement as of the date
first written above.

                                            By:
                                               ---------------------------------
                                               Charles E. Underbrink, individual

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