In case any such bonds shall be issued for the purpose of paying any such sums required to be paid by a court on account of or in respect of the purchase or acquisition by such city of any waterworks, gas works, electric light works or property from which such city may thereafter derive any income or revenue, such income and revenue for each year shall be used to pay the cost of maintaining, repairing, enlarging and extending such works or property, and the interest on such bonds, and the residue of such income and revenue shall be paid into the sinking fund provided for by section 95.480, for the payment of the principal of such bonds.