The commissioner, at his discretion, may rent the building or parts thereof for exhibition purposes, at reasonable rates, giving first preference to exhibitors of this state. The commissioner may also rent the building, or any parts thereof, for the purpose of storage or other uses, as necessary for supplemental income to help defray operating expenses. From the income received he shall pay the expenses and operating charges of the building, which may include a reasonable sum for insurance and improvements; any remaining balance shall be deposited with the state treasurer in a separate fund for the purposes of the eastern states building.