The agreement between the board and the participating counties or other authorized agency shall provide that a fair and proportionate part of the expense of the board administering this chapter shall be considered a part of the cost of the development or operation of the planned development, and such costs shall be paid into a separate state fund in the state treasury, to be known as the "state inland ports fund." Such fund shall be used by the board for the promotion, development, construction, improvement, expansion, maintenance, advertising, and general advancement of the state harbors, ports, rivers, channels, and waterways and may be expended on requisition of the board for such purposes and such other purposes as in the opinion of the board is to the best interest of the ports, harbors, and waterways of this state. The salaries of all officers, employees, or agents of the board, performing duties required by this chapter, and all other expenses incidental to the port, harbor, or waterway operation of the board shall be fixed by the board and payable out of said fund. The board may contract with one or more state inland port authorities, or any city, county or other authorized port or harbor agency for any joint activity or for the joint employment of personnel with the expense of the activity or salary of such personnel to be paid by the board from operational funds provided by the contracting parties.