Mich. Comp. Laws § 42.18: Joint action with other governmental unit or agency.

Sec. 18.

Each charter township may join with any governmental unit or agency, or with any number or combination thereof, by contract or otherwise as may be permitted by law, to perform jointly, or by one or more, for or on behalf of the other or others, any power or duty which is permitted to be so performed by law or which is possessed or imposed upon each such governmental unit or agency.