[Proceeds from sale of bonds; building and improvement

fund; expenditures.] That the proceeds from the sale of said bonds shall be paid to the secretary and treasurer of the board issuing same, and shall by such secretary and treasurer be placed in a separate fund to be known as "building and improvement fund" to be used and paid out only for the specific purposes in this act enumerated upon order of the board, or checks signed by the president or vice-president of the board and by the secretary and treasurer thereof, except such portion thereof as may have been received on account of accrued interest of said bonds to date of delivery, which amount shall be placed in the "interest and retirement fund" for the liquidation of said bonds as hereinafter provided. The cost of preparing, advertising and selling said bonds, including any necessary expense for legal opinions thereon, shall be paid out of the proceeds of the sale of said bonds.