The name of a city or town in the county shall be printed upon the ballot if there has been filed at least twenty days before the election a petition signed by qualified electors of the county equal in number to at least five per cent of the total number of votes cast within the county for governor at the last preceding general election, praying that the name of such city or town be placed on the ballot. Before the name of a city or town may be printed on the ballot, the chief officer and governing body of the city or town shall file with the board a statement signed by the chief officer designating one or more sites for the proposed courthouse, which shall be in or conveniently near the city or town, and shall describe the area of each site and the price at which each can be obtained, together with an offer from the owner agreeing to sell at such price. If any such city or town is chosen as the county seat, the board shall purchase one of the sites so designated, if suitable for construction of the courthouse, at a price not exceeding the sum mentioned in the statement.