Mich. Comp. Laws § 500.5804

Sec. 5804. (1) Any number of persons, not less than 20, a majority of whom shall be bona fide residents of this state, by complying with the provisions of this chapter, may become together with others who may hereafter be associated with them or their successors, a body corporate, for the purpose of carrying on the business of mutual insurance as herein provided. (2) Any persons proposing to form any such insurer shall subscribe and acknowledge articles of incorporation in accordance with chapter 50.