Each incorporator of a cooperative shall be a member thereof, but no other person may become a member thereof unless such other person agrees to use electric energy or other services furnished by the cooperative when they are made available through its facilities. Any member of a cooperative who agrees to use electric energy shall cease to be a member if he does not use electric energy supplied by the cooperative within six months after it has been made available to him or if electric energy is not made available to him by the cooperative within two years after he becomes a member, or within such lesser period as the bylaws of the cooperative may provide. A husband and wife may hold a joint membership in a cooperative. Membership in a cooperative shall not be transferable, except as provided in the bylaws. The bylaws may prescribe additional qualifications and limitations in respect of membership.