No city, town, or other municipal corporation having a population of less than six thousand, except as hereafter provided, shall become indebted in an amount including present indebtedness, exceeding five per centum of the assessed value of the property therein, except for the construction of or purchase of water works, gas, or electric lighting plants, or sewerage, or for the improvement of streets, for which purposes an additional indebtedness not exceeding three per centum may be created; provided, this limitation shall not affect any debt now authorized by law to be created, nor any temporary loans to be paid within one year, made in anticipation of the collection of taxes, not exceeding one-fourth of the annual revenues of such city or town. All towns and cities having a population of six thousand or more, also Gadsden, Ensley, Decatur, and New Decatur, are hereby authorized to become indebted in an amount including present indebtedness, not exceeding seven per centum of the assessed valuation of the property therein, provided that there shall not be included in the limitation of the indebtedness of such last described cities and towns the following classes of indebtedness, to wit: Temporary loans, to be paid within one year, made in anticipation of the collection of taxes, and not exceeding one-fourth of the general revenues, bonds, or other obligations already issued, or which may hereafter be issued for the purpose of acquiring, providing, or constructing school houses, water works, and sewers; and obligations incurred and bonds issued for street or sidewalk improvements, where the cost of the same, in whole or in part, is to be assessed against the property abutting said improvements; provided, that the proceeds of all obligations issued as herein provided, in excess of said seven per centum shall not be used for any purpose other than that for which said obligations were issued. Nothing contained in this article shall prevent the funding or refunding of existing indebtedness. This section shall not apply to the cities of Sheffield and Tuscumbia.