Upon securing possession of the properties covered by the lease agreement, the board is authorized to and shall thereafter operate, manage and control the said properties for the purpose of conducting or permitting to be conducted thereat livestock shows, agricultural and industrial displays, markets and other exhibits and events related thereto and to make contracts with individuals, livestock associations and other organizations for the conduct of such shows, displays, markets, exhibits and events related thereto. The board is authorized to make such charges for and in connection with any of said matters as will produce revenues sufficient to pay the rentals required to be paid by the board under the lease agreement and to pay the reasonable expenses of operating the said properties and the board's administrative expenses including salaries and per diem, all to the end that the said properties shall be self-supporting; provided, however, that such charges shall not be made with a view of producing any revenue or profit to the board or to the State of Alabama but shall be based exclusively upon the rentals required to be paid by the board under the lease agreement, the reasonable expenses of operating the properties covered thereby and the board's administrative expenses. It is hereby declared that it is not intended that this article shall be interpreted as authorizing the board to engage in the business of selling or marketing livestock or products of any kind or in what may be termed a brokerage business or to compete with private enterprise. In the event the revenues derived during any fiscal year of the board from the operation of the properties covered by the lease agreement should be in excess of the said rentals and operation and administration expenses payable during the same fiscal year, then the said charges shall be adjusted for the ensuing fiscal year in such manner as to void as far as may be practicable the production of any excess over the amount necessary to pay the said rentals and operating and administrative expenses payable during such ensuing fiscal year. If during any fiscal year the said charges should produce any such excess, then such excess shall be used to make advance payments on the rentals payable under the lease agreement.