<PAGE>   1
                                                                   Exhibit 10.61

Member Name:                                          Member #:
            ---------------------------------------            -----------------
                                                                   

                              MEMBERSHIP AGREEMENT
                    (NATIONAL MEMBERSHIP WITH FLEXIBLE DUES)

                           RETAIL INSTALLMENT CONTRACT

1. DEFINITION OF TERMS. "You" and "your" refer to the individual purchaser or
purchasers who have signed this Agreement. "We", "us", and "our" refer to
Thousand Trails, Inc. ("Trails") and National American Corporation and its
subsidiaries ("NACO"). "Disclosure Statement" means the booklet containing
information on our membership program that was attached to this Agreement and
delivered to you at the time of your purchase. "Preserves" mean the recreational
campground resorts owned or operated by Trails and the recreational campground
resorts owned or operated by NACO for the benefit of their respective
memberships. "Member Rules" mean the rules and other terms set forth in our
Campground Directory, which govern the use of the preserves by our members. A
copy of our Campground Directory was delivered to you at the time of your
purchase.

2. WHAT YOU ARE PURCHASING. You are purchasing a NATIONAL CAMPING MEMBERSHIP
which entitles you to use all Trails and NACO preserves on the terms set forth
herein. The preserves that are currently available for use by members are
described in the Disclosure Statement.

The initial term of your membership is three (3) years following the date of
your purchase. After this initial term, the term of your membership will
automatically renew for additional one-year periods ("renewal terms" herein)
unless you notify us in writing of your desire to terminate your membership at
least 60 days prior to the expiration of the initial term or renewal term, as
the case may be.

3. TERMS OF MEMBERSHIP. During the term of your membership, you are entitled to
use all preserves that are designated by Trails and/or NACO as available for use
by members and included in your membership, subject to the following:

You must use the preserves in accordance with this Agreement and the Member
Rules. We have Member Rules regarding, among other things: (a) advance
reservation or first-come, first-choice space arrangements; (b) length of stay;
(c) frequency of use; (d) charges for benefits or services, including rental
units, pet fees, food services, goods purchased, gasoline, and other services
made available by us from time to time; (e) restrictions on guest visits,
including number of guests allowed and guest fees; (f) length of season for use
of the preserves; (g) hours of operation of facilities; (h) use of preserves by
non-members in connection with programs sponsored by us, including without
limitation, our marketing and sales programs, SuperHost group rentals,
charitable functions, community groups and other public use scheduled so as not
to conflict with member use; and (i) such other matters and restrictions on use
as may be reasonably necessary to ensure maximum availability of any preserve
for use by our membership as a whole. We reserve the right, in our sole
discretion, to add, modify, or delete Member Rules from time to time as we may
deem appropriate. Please consult the current Member Rules if you have questions
regarding use of the preserves.

It is your responsibility to use the preserves in a safe and reasonable manner
and to observe the Member Rules. You are also responsible for the conduct of
your children and guests and you are liable for all damages caused by the
negligent or reckless use, or intentional misuse, of the preserves by you or
your children.

The location of, and facilities and amenities at, all of Trails' and NACO's
preserves are described in the Disclosure Statement and are subject to change by
Trails and NACO. Preserves and facilities may be added to or subtracted from
those which existed at the time of execution of this Agreement. Trails and NACO
are under no obligation to increase the number of or improve existing preserves.
Trails and NACO reserve the right to sell memberships with rights and privileges
different from your membership.

Your membership constitutes merely a contractual license to use the facilities
provided by Trails and/or NACO from time to time at the preserves where you have
membership rights. Such preserves and facilities are subject to change as
provided in this Agreement and your membership does not constitute an interest
in, is not secured by, and does not entitle you to any recourse against any real
property of Trails or NACO, nor are you entitled to vote on any aspect relating
to the businesses of Trails or NACO or to share in any of the profits of the
businesses of Trails or NACO. The application and use of all amounts paid by you
under this Agreement, including your purchase price and annual dues, is within
our sole discretion.

You may not possess, hold, or own more than one membership in either Trails or
NACO, and if you acquire more than one membership under any circumstances, we
will terminate all memberships held by you in excess of one.

4. TRANSFERABILITY. Your National Membership is transferable, subject to the
following limitations. A National Membership: (a) may only be resold for a price
which does not exceed the price paid by you for your membership plus a
reasonable transfer fee as set forth below; (b) may be transferred only if the
purchase price for your membership is paid in full and your annual dues are
current at the time of transfer; and (c) may be transferred only if your
transferee agrees to accept the rate of annual dues and use fees charged by us
on new sales of similar memberships and the Member Rules in effect at the time
of transfer. A National Membership cannot be divided and, if you transfer one,
or if one is transferred by operation of law, as in the event of divorce,
inheritance, descent, or attachment, all membership privileges must be
transferred together.

In connection with any transfer of a National Membership, we will charge a
reasonable transfer fee, which is currently $750. A transfer may be effected
only with our prior written consent, which we will not unreasonably withhold. A
transfer will not become effective until: (a) you and your prospective
transferee have represented to us in writing that the transfer is in compliance
with the foregoing terms; and (b) your prospective transferee has entered into a
new membership agreement.

We will not purchase your membership and we can provide no assurance that we
will be able to locate a buyer for your membership in the event it is
transferable and you decide to sell it. In addition to our sale of new
memberships in company sales programs, we currently offer a resale program
pursuant to which we attempt to resell previously-owned memberships on behalf of
the selling member. In order to participate in our resale program, the selling
member must have paid the purchase price of his membership in full and must be
current on his annual dues. We reserve the right to modify or discontinue our
resale program at any time without further notice and without incurring any
legal liability for the modification or discontinuation.

You may not transfer or sell your membership or assign, rent, loan, or otherwise
alienate your membership, temporarily or permanently, in any manner other than
as provided in this section. Any transfer in violation of this prohibition shall
be null and void. In the event of any dispute over ownership of your membership,
we may, without liability to any person and without releasing you 


                                  Page 1 of 4

<PAGE>   2

Member Name:                                          Member #:
            ---------------------------------------            -----------------

from your financial obligations to us, suspend and refuse membership privileges
to all persons claiming rights to the membership until they have resolved the
dispute in a manner satisfactory to us and communicated the resolution to us in
writing.

5. DEFAULT AND REMEDIES. Time is of the essence of this Agreement and any of the
following events will be "an event of default":

     (a)  Your failure to make any payment under this Agreement when due,
          including but not limited to the payment of the application fee,
          purchase price, finance charge, and annual dues, or
     (b)  The falsity of any representation made by you in this Agreement or
          your credit application, or 
     (c)  A material breach by you of any provision of this Agreement or the
          Member Rules.

Should any "event of default" occur, we may immediately suspend your membership
rights. In addition, upon the occurrence of any "event of default", we may, upon
30 days' written notice to you, declare the entire unpaid principal balance of
the purchase price, together with the finance charge and annual dues accrued to
the date of default, immediately due and payable. Moreover, we may continue to
collect annual dues from you as they accrue for the balance of the initial term
or renewal term, as the case may be. In the alternative, we may, upon the
occurrence of any "event of default", and upon 30 days' written notice to you,
terminate this Agreement and your membership. If we terminate this Agreement and
your membership because of your default, which we may, but are not required to
do, we shall have all remedies provided by law. If any payment required by this
Agreement is not made in full within ten days of its due date, you agree to pay
us a late charge in the amount set forth in paragraphs 11 and 12. In addition,
where permitted by law, reasonable collection charges will be imposed if any
payment required by this Agreement is not made in full within 30 days of its due
date and collection efforts are made. If permitted by law, a reasonable fee will
also be imposed for processing any check or other payment that is returned
unpaid. If this Agreement is referred to an attorney for collection after your
default, or if a legal action is commenced to enforce or declare the meaning of
any provision of this Agreement, the prevailing party will be awarded its
reasonable attorney's fees and costs, including fees and costs incurred in both
trial and appellate courts.

6. ASSIGNMENT. We may sell or assign this Agreement, and any such assignment may
vest in our assignee all of our right, title, and interest in this Agreement,
and all payments required to be made by you under this Agreement may be required
to be paid to such assignee. No transfer, extension, or assignment of any
interest under this Agreement will release you from your obligation to make all
payments required under this Agreement.

7. CREDIT APPLICATION AND REPORTING. If this Agreement provides for an
installment purchase, the Agreement may be rescinded by us, in our sole
discretion, unless your application for credit is approved by our corporate
office. If your credit application is not approved, we will notify you in
writing within 30 days. You agree that we may from time to time seek and receive
credit related information about you from others such as stores, other
creditors, and credit reporting agencies. You also agree that we may furnish on
a regular basis credit and experience information regarding your account to
others seeking that information. You represent that all information supplied to
us is true, that you are of legal age, that the address set forth on page 4 of
this Agreement is your permanent residence address, and that you are acquiring
this membership solely for the personal enjoyment of you and your family.

8. MISCELLANEOUS. This Agreement contains the entire agreement between you and
us. No waiver or modification of any of the terms or conditions of this
Agreement shall be effective unless in writing and signed by you and an
authorized representative of our corporate office. The terms of this Agreement
will benefit and bind the respective heirs, executors, administrators, legal
representatives, successors, assigns, and transferees of the parties. Any
provision of this Agreement which proves to be invalid, void, or illegal will
not affect, impair, or invalidate any other provision of this Agreement and such
other provisions will remain in full force and effect.

9. APPLICATION FEE. An application fee of $150.00, plus applicable taxes, is
payable as set forth in section 11. This application fee is designed to cover
the costs we incur in processing your membership application and related
paperwork, setting up your membership in our computer system, and issuing you a
membership card that works with our CIS system.

10. PURCHASE PRICE. The purchase price for your membership is
$_________________, plus applicable taxes, and is payable as set forth in
section 11.

                                  Page 2 of 4

<PAGE>   3

Member Name:                                          Member #:
            ---------------------------------------            -----------------


11. METHOD OF PAYMENT. (CHECK ONLY ONE AND INITIAL.)


                    [ ]    I desire to pay the total application fee and 
------------------         purchase price for my membership of $_______________
(Buyer's Initials)         in full on the day of purchase.

                    [ ]    I desire to pay the total application fee and 
------------------         purchase price for my membership in installments, as
(Buyer's Initials)         follows: (IF CHECKED, COMPLETE THE BALANCE OF SECTION
                           11.)

If you are financing, a cash down payment of $________ is due on the day of
purchase. The remaining balance of $_________ will accrue interest on the
declining principal balance at the rate of 14.9% per annum, and will be payable
in [ ] 12 (twelve), [ ] 24 (twenty-four), or [ ] 36 (thirty-six) equal
consecutive monthly installments of $________ each, including interest. These
payments will commence on the__ day of____, 19___, and will continue on the same
day of each month thereafter until the principal balance and accrued interest
thereon are paid in full. All payments are stated and must be made in U.S.
Dollars.


<TABLE>
<CAPTION>
-----------------------------------------------------------------------------------------------------------------------------------
<S>                        <C>                       <C>                        <C>                       <C>                  
ANNUAL PERCENTAGE RATE     FINANCE  CHARGE           AMOUNT FINANCED            TOTAL OF PAYMENTS         TOTAL SALE PRICE
The cost of your credit    The dollar amount the     The amount of credit       The amount you will have  The total cost of your
as a yearly rate.          credit will cost you.     provided to you or on      paid after you have paid  purchase on credit
                                                     your behalf.               all payments as           including your down
                                                                                scheduled.                payment of
                                                                                                          $              
                                                                                                           --------------
              %            $                         $                          $                         $              
--------------              ---------------           ---------------            ---------------           --------------
-----------------------------------------------------------------------------------------------------------------------------------

Your payment schedule will be:      Number of Payments:         
                                                                 ------------------------

                                    Amount of Monthly Payment:  $
                                                                 ------------------------

                                    Payments are due monthly beginning:
                                                                        -----------------

LATE CHARGE: If a payment is late by ten or more days, you will be charged 5% of
the delinquent installment or $5.00, whichever is less. 

PAC PLAN: The interest rate disclosed above will automatically increase by 3%
(which is the maximum increase) in the event any one of the following occurs:
(a) you discontinue participation in our preauthorized check (PAC) plan, (b)
your financial institution is unable to participate, or (c) we discontinue your
participation for a reasonable cause. The interest rate will not increase above
17.9%. An increase in the interest rate would increase your monthly payment by
not more than $2.00.

PREPAYMENT: If you pay off early, you will not have to pay a penalty. See the
other provisions of this Agreement for additional information about nonpayment,
default, our right to accelerate the maturity of this obligation, and
prepayment.
-----------------------------------------------------------------------------------------------------------------------------------
</TABLE>

ITEMIZATION OF THE AMOUNT FINANCED:
(1)  Application Fee                                        $
                                                             ---------------
(2)  Purchase Price of Your Membership                      $
                                                             ---------------

(3)  Less Down Payment                                      $
                                                             ---------------

(4)  Amount Financed  (Sum of items 1 & 2, less item 3)     $
                                                             ---------------

12. DUES. During the initial term and each renewal term of your membership, you
agree to pay us annual dues in the amount set forth below for the dues option
("Dues Option") you select (CHECK ONLY ONE AND INITIAL). Applicable taxes, if
any, will be added to your annual dues. You may change from one Dues Option to
another Dues Option one time for each calendar year, provided that you give us
written notice of your desire to change options no later than November 1 of the
year prior to the year for which you desire the change to be effective.


                    [ ]  ADVENTURER: 30 NIGHTS FOR $329 PER YEAR (entitles you 
-----------------        to camp overnight at the preserves included (Buyer's 
(Buyer's Initials)       Initiate your membership for a total of 30 nights in a 
                         calendar year and also includes unlimited day use of 
                         these preserves).

                    [ ]  EXPLORER: 50 NIGHTS FOR $441 PER YEAR (entitles you to
-----------------        camp overnight at the preserves included in your 
(Buyer's Initials)       membership for a total of 50 nights in a calendar year
                         and also includes unlimited day use of these 
                         preserves).


                    [ ]  ON THE ROAD: UNLIMITED USE FOR $1,200 PER YEAR 
-----------------        (entitles you to unlimited overnight camping at the 
(Buyer's Initials)       preserves included in your membership (subject to 
                         length of stay restrictions for any one preserve) and 
                         to unlimited day use of these preserves).

BY SIGNING THIS AGREEMENT, YOU ARE MAKING A LEGAL COMMITMENT TO PAY ANNUAL DUES
FOR A MINIMUM OF THREE YEARS.

Your annual dues will be prorated for the period from the date of this Agreement
through December 31 of the year in which this Agreement is executed. Thereafter,
your annual dues are payable in full on or before January 1 of each year. As a
convenience, you may pay the annual dues in two semi-annual installments or four
quarterly installments. Each of the installment payments will be subject to a
processing fee in an amount set by us. This processing fee, which is subject to
increase, is currently $5 for each installment payment. If payment of your
annual dues is late by ten or more days, you will be assessed a late charge in
the maximum amount permitted for late charges under the retail installment sales
law in effect in the state of your residence. Your annual dues are stated and
must be paid in U.S. Dollars.

DUES INCREASES. The amount of annual dues payable under each Dues Option may be
increased each year, upon thirty (30) days advance written notice, by the
percentage increase in the Consumer Price Index for the calendar year prior to
the year for which the increase is being made. Consumer Price Index means the
consumer price index for all urban consumers as reported by the United States
Department of Labor, Bureau of Labor Statistics. 

USE FEES. If you desire to camp overnight for more nights than are included in
the Dues Option you select, you agree to pay a use fee equal to (i) $16.00 per
additional night if you are camping in your own recreational vehicle, or (ii)
$12.00 per additional night if you 


                                  Page 3 of 4

<PAGE>   4

Member Name:                                          Member #:
            ---------------------------------------            -----------------

are camping in a tent. The terms "recreational vehicle" and "tent" are defined
in the Member Rules. The amount of these use fees may be increased from time to
time by the cumulative percentage increase in the Consumer Price Index since the
date of the last increase. If you rent a trailer or cabin during your stay, this
use fee will be included in the rental fee for the trailer or cabin. The stated
amount of the use fees include any applicable taxes.

NOTICE: ANY HOLDER OF THIS CONSUMER CREDIT CONTRACT IS SUBJECT TO ALL CLAIMS AND
DEFENSES WHICH THE DEBTOR COULD ASSERT AGAINST THE SELLER OF GOODS OR SERVICES
OBTAINED PURSUANT HERETO OR WITH THE PROCEEDS HEREOF. RECOVERY HEREUNDER BY THE
DEBTOR SHALL NOT EXCEED AMOUNTS PAID BY THE DEBTOR HEREUNDER.

NOTICE TO THE BUYER: (1) DO NOT SIGN THIS AGREEMENT BEFORE YOU READ IT OR IF IT
CONTAINS ANY BLANK SPACES TO BE FILLED IN. (2) YOU ARE ENTITLED TO A COMPLETELY
FILLED IN COPY OF THIS AGREEMENT. (3) YOU CAN PREPAY THE FULL AMOUNT DUE UNDER
THIS AGREEMENT AT ANY TIME. (4) IF YOU DESIRE TO PAY OFF IN ADVANCE THE FULL
AMOUNT DUE, THE AMOUNT WHICH IS OUTSTANDING WILL BE FURNISHED UPON REQUEST. (5)
EACH PERSON SIGNING THIS AGREEMENT AS A MEMBER SHALL BE JOINTLY AND SEVERALLY
LIABLE FOR ALL OF YOUR OBLIGATIONS. (6) YOU ACKNOWLEDGE THAT YOU HAVE READ AND
RECEIVED A COPY OF THIS AGREEMENT, THE DISCLOSURE STATEMENT AND OUR CAMPGROUND
DIRECTORY .

                                  YOUR INITIALS              /
                                               -----------------------------

IF YOU HAVE BEEN PERSONALLY SOLICITED, AND YOUR AGREEMENT OR OFFER TO PURCHASE
IS MADE AT A PLACE OTHER THAN OUR PLACE OF BUSINESS, YOU MAY CANCEL THIS
AGREEMENT AS SET FORTH BELOW.

YOU, THE BUYER, MAY CANCEL THIS TRANSACTION AT ANY TIME PRIOR TO MIDNIGHT OF THE
THIRD BUSINESS DAY AFTER THE DATE OF THIS TRANSACTION. SEE THE ATTACHED NOTICE
OF CANCELLATION FORM FOR AN EXPLANATION OF THIS RIGHT.

                  CHECK ONE:      APPLICABLE [ ]   NOT APPLICABLE [ ]

EVEN IF THE FOREGOING RIGHT OF CANCELLATION IS NOT APPLICABLE, YOU MAY CANCEL
THIS AGREEMENT AS SET FORTH BELOW.

                             NOTICE OF CANCELLATION


YOU MAY CANCEL THIS CONTRACT, WITHOUT ANY PENALTY OR OBLIGATION, WITHIN THREE
BUSINESS DAYS FROM THE DATE THE CONTRACT IS EXECUTED. TO CANCEL THIS CONTRACT,
MAIL OR DELIVER A SIGNED AND DATED COPY OF THIS CANCELLATION NOTICE OR A COPY OF
THIS CONTRACT IF IT CONTAINS THE CANCELLATION INSTRUCTIONS, OR ANY OTHER WRITTEN
NOTICE, OR SEND A TELEGRAM TO THOUSAND TRAILS, INC., AT 2711 LBJ FREEWAY, SUITE
200, DALLAS, TEXAS 75234; ATTENTION: CONTRACT PROCESSING, NOT LATER THAN
MIDNIGHT OF

                                            .
--------------------------------------------
                  (Date)


I HEREBY CANCEL THIS TRANSACTION                  .
                                ------------------
                                         (Date)

                                            -----------------------------------
                                                  (Purchaser's Signature)

WITH THE NOTICE OF CANCELLATION, OR SEPARATELY IF A TELEGRAM IS SENT, YOU MUST
RETURN THE ORIGINAL MEMBERSHIP CAMPING CONTRACT, MEMBERSHIP CARD AND ALL OTHER
EVIDENCE OF MEMBERSHIP TO THE SELLER. YOU SHOULD PROMPTLY RETURN THESE DOCUMENTS
WITH THE NOTICE OF CANCELLATION, OR SEPARATELY IF A TELEGRAM IS SENT. FAILURE TO
SEND THE DOCUMENTS PROMPTLY COULD DELAY YOUR REFUND. YOU SHOULD RETAIN FOR YOUR
RECORDS ONE COPY OF THE CANCELLATION NOTICE, OR A CARBON OF THE CONTRACT WHEN IT
PROVIDES THE CANCELLATION INFORMATION, OR OTHER WRITING SHOWING INTENT TO
CANCEL. MAILING BY ORDINARY MAIL IS ADEQUATE BUT CERTIFIED MAIL RETURN RECEIPT
REQUESTED IS RECOMMENDED.

NAME:                              ADDRESS:
     -----------------------------         ------------------------------------

CITY:                                    STATE:             ZIP:
     -----------------------------------       -----------      ---------------

EXECUTED THIS                        DAY OF                19
             ------------------------      ---------------   -----------

                                               Membership Campground Operator:

------------------------------------------     
        Purchaser's Signature                 ---------------------------------
                                                  2711 LBJ Freeway, Suite 200
                                                  Dallas, Texas  75234

------------------------------------------
        Purchaser's Name (please print)

------------------------------------------    ---------------------------------
        Purchaser's Signature                    Authorized Signature


------------------------------------------    ---------------------------------
        Purchaser's Name (please print)                  Preserve


                                  Page 4 of 4