"(Article XI) Section 3. Cities and villages organized pursuant to state law are hereby empowered, to determine their local affairs and government, subject only to this constitution and to such enactments of the legislature of state-wide concern as shall with uniformity affect every city or every village. The method of such determination shall be prescribed by the legislature. No county, city, town, village, school district or other municipal corporation may become indebted in an amount that exceeds an allowable percentage of the taxable property located therein equalized for state purposes as provided by the legislature. In all cases the allowable percentage shall be five per centum except as follows: (a) For any city authorized to issue bonds for school purposes, an additional ten per centum shall be permitted for school purposes only, and in such cases the territory attached to the city for school purposes shall be included in the total taxable property supporting the bonds issued for school purposes. (b) For any school district which offers no less than grades one to twelve and which at the time of incurring such debt is eligible for the highest level of school aids, ten per centum shall be permitted. Any county, city, town, village, school district, or other municipal corporation incurring any indebtedness as aforesaid, shall before or at the time of doing so, provide for the collection of a direct annual tax sufficient to pay the interest on such debt as it falls due, and also to pay and discharge the principal thereof within twenty years from the time of contracting the same; except that when such indebtedness is incurred in the acquisition of lands by cities, or by counties having a population a[ one hundred fifty thousand or over, for public, municipal purposes, or for the permanent improvement thereof, the city or county incurring the same shall, before or at the time of so doing, provide for the collection of a direct annual tax sufficient to pay the interest on such debt as it falls due, and also to pay and discharge the principal thereof within a period not exceeding fifty years from the time of contracting the same. An indebtedness created for the purpose of purchasing, acquiring, leasing, constructing, extending, adding to, improving, conducting, controlling, operating or managing a public utility of a town, village or, city or special district, and secured solely by the property or income of such public utility, and whereby no municipal liability is created, shall not be considered an indebtedness of such town, village or, city or special district, and shall not be included in arriving at such five or eight per centum debt limitation.