The cost and expense of acquiring land for, erecting, equipping, furnishing, and maintaining a joint city-county building shall be borne by such county and city in the proportion determined by the county board of the county and the city council of the city of the first class. The building shall not be erected or contracted to be erected, no land shall be acquired therefor, and no bonds shall be issued or sold by the county or the city of the first class until the county and the city of the first class have each been authorized to issue bonds to defray its proportion of the cost of such land, building, equipment, and furnishings by the required number of electors of the county and the city of the first class in the manner provided by sections 16-6,100 and 23-3501.