The provisions of sections 13-601 to 13-603 are supplementary to existing laws relating to any unit of local government and confer upon such units of local government powers not previously granted by state law to permit those governmental subdivisions to use such funds and other available resources for the purposes of sections 13-601 to 13-603, and any unit of local government shall have the power to join with any other governmental subdivision, or with any agency or nonprofit corporation, whether federal, state, or local, or with any number or combinations thereof, by contract or otherwise, in joint ownership, operation of any function, or exercise of any power pursuant to the provisions of sections 13-601 to 13-603, or in agreements containing the provision that one or more operate or perform for the other or others.