The board of supervisors of any class one county which has a population in the 1970 decennial census of not less than thirty-five thousand (35,000) and not more than fifty thousand (50,000) and having a total assessed valuation in 1971 of not less than forty million dollars ($40,000,000.00) and not more than fifty million dollars ($50,000,000.00) may impose an excise and/or transfer tax upon the sale or construction of all new family units as defined in Section 37-57-111 for capital improvement of public schools as provided by law for countywide public school districts. Said taxation shall not exceed three percent (3%) of the first twenty thousand dollars ($20,000.00) and one-half of one percent (1/2 of 1%) of all over twenty thousand dollars ($20,000.00) of the total sale or contract price of the family unit; however, said taxation shall not exceed three percent (3%) of the first ten thousand dollars ($10,000.00) and one-half of one percent (1/2 of 1%) of all over ten thousand dollars ($10,000.00) of the total sale or contract price of apartments, condominiums, duplexes or townhouses.
The tax hereby authorized, if imposed by order of the board of supervisors of the county by order duly spread upon the minutes of said board, shall apply only to the initial sale or construction of new family units not heretofore occupied or used for residence purposes, and shall be an indebtedness of the owner of the family unit.
Said tax shall not apply to such family units purchased or constructed by or for any religious, charitable, educational or nonprofit corporation or institution, nor shall it apply to demonstration of model homes.