If the purpose set forth in an interlocal agreement is the acquisition, construction, or operation of a revenue-producing facility, the agreement may provide for the repayment or return to the parties of all or any part of the contributions, payments, or advances made by the parties pursuant to section 5, and may provide for payment to the parties of any additional sum or sums derived from the revenues of the facility irrespective of whether such contributions, payments, or advances are required to be paid, repaid, or returned from revenues of the facility. Payments, repayments, or returns shall be made at any time and in the manner specified in the agreement, and may be made at any time on or prior to the rescission or termination of the agreement, or completion of the purposes of the agreement.