Whenever bonds are issued by the Board of Trustees, as provided in this Act, it shall be the duty of such Board to establish a charge or fee for the use of any such building or buildings sufficient at all times to pay maintenance and operation costs and principal of and interest on such bonds, and all revenues derived from the operation thereof shall be set aside in a separate account and fund which shall be used only in paying the cost of maintenance and operation, and paying the principal of and interest upon the bonds issued for the purpose or purposes set forth and described in the resolution authorizing the issue of said bonds, and such charges or fees shall be sufficient at all times for such purposes.
110 ILCS 420/5