For the purpose of providing funds for the acquisition, construction, erection, equipment and furnishing of hospitals, nursing or convalescent homes, and related facilities, including medical office buildings to provide offices for rental to physicians or dentists on a hospital’s medical staff, and for providing sites therefor, including offstreet parking space, and making from time to time enlargements or extensions thereof, the city council, upon recommendation and request of the board of trustees created pursuant to sections 96.150 to 96.220, may issue and sell revenue bonds. In addition to pledging the net income and revenues as herein provided, the council and board, in their discretion, may mortgage, by mortgage or deed of trust, the real and personal property comprising the project or portions thereof for the payment of the bonds, both principal and interest. The revenue bonds are payable, both as to principal and interest, solely and only out of the net income and revenues arising from the operation of the facility, after providing for the costs of operation and maintenance thereof, or from other funds made available to the facility from sources other than from proceeds of taxation, or from proceeds of foreclosure sale of property mortgaged or pledged as security therefor.