Section 15.
The debt of any county, township, city, town, school district or any other political subdivision, shall never exceed five per centum upon the assessed value of the taxable property therein; provided that any incorporated city may, by a two-thirds vote, increase such indebtedness three per centum on such assessed value beyond said five per centum limit, and a school district, by a majority vote may increase such indebtedness five percent on such assessed value beyond said five per centum limit; provided also that any county or city by a majority vote may issue bonds upon any revenue-producing utility owned by such county or city, or for the purchasing or acquiring the same or building or establishment thereof, in amounts not exceeding the physical value of such utility, industry or enterprise. In estimating the indebtedness which a city, county, township, school district or any other political subdivision may incur, the entire amount, exclusive of the bonds upon said revenue-producing utilities, whether contracted prior or subsequent to the adoption of this constitution, shall be included; provided further that any incorporated city may become indebted in any amount not exceeding four per centum of such assessed value without regard to the existing indebtedness of such city for the purpose of constructing or purchasing waterworks for furnishing a supply of water to the inhabitants of such city, or for the purpose of constructing sewers, and for no other purposes whatever. All bonds and obligations in excess of the amount of indebtedness permitted by this constitution, given by any city, county, township, town, school district, or any other political subdivision shall be void.