Mich. Comp. Laws § 141.166

Sec. 6. A public corporation shall not be required to have issued or incurred 1 or more tax obligations to be supported by 1 or more unlimited tax pledges before the election at which the question of making the pledges is submitted, and a public corporation may conduct the election either before, concurrently with, or after issuing or incurring a tax obligation. A public corporation may make an unlimited tax pledge in support of a tax obligation before the election to approve the pledge, but a pledge shall not be binding on the public corporation until the question of making the pledge has been approved by the electors of the public corporation as provided in section 4.