Mich. Comp. Laws § 141.382
The bonds or notes authorized to be issued under this act shall be issued in the name of the county, city, township, or village and shall be executed in the manner provided by resolution of its legislative body. Bonds or notes issued under this act shall be negotiable instruments with the last maturity due not later than the year in which the final payment is due according to the contract of sale of capital assets. The maximum principal and interest falling due in any year shall not exceed income to be received during that year from the contract of sale of capital assets pledged for the payment of the bonds or notes plus any income due in prior years that will not be required for payment of principal or interest, or both, in prior years. The due date of principal and the first interest payment in each year shall be not less than 30 days subsequent to the estimated time of receipt of the payments on the contract for sale of capital assets pledged. The bonds and coupons and notes shall be exempt from taxation by this state or by any taxing authority within this state.
MCL 141.382