When improvements are constructed by two or more districts, bids may be jointly called for and opened and considered at the designated office of either district, and the directors of such districts shall approve the letting of the contract and contractor’s bond, and may meet and transact all business for that or any other purpose concerning such project at a place outside the district, or at any office established for such joint project. All bids, bonds, contracts, etc., of said project shall be in the name of said districts, which are empowered to do all acts by joint action that one district may do, the action of each district being determined by its directors. A general manager, who may be a director of either district, may be employed for such project, whose duties may be set forth in the joint ownership contract.