Such property may be used for any useful public purpose, and by resolution of the legislative body of any village and/or township and/or city, any portion of any real estate or building, may be leased or otherwise let to the local school board for educational purposes, and may also be rented by day to day agreement for educational, charitable or entertainment purposes. The revenue from any such rentals shall be applied in the payment of any installment, and/or the interest thereon, until the purchase price of such property is wholly paid for, or for the maintenance and improvement of the same. Thereafter such revenues shall be covered into the general fund of such village and/or township and/or city.