Mich. Comp. Laws § 560.201b

Sec. 201b. Notwithstanding the conditions specified in section 201(1), an assessor's plat complying with sections 201 to 213 may also be ordered by the governing body of a municipality if all of the following conditions are met: (a) When a parcel or tract of land had been improved by 4 or more permanent residential structures before January 1, 1968. (b) When division of the parcel or tract into lots for the purpose of selling or leasing the permanent residential structures thereon would result in a lot size or configuration smaller than required by this act or by local ordinance. (c) Each lot be serviced by a sewage disposal and water supply system approved by the local health department having jurisdiction.