Lawrence county may become indebted and may issue bonds therefor in an amount not exceeding $130,000 in addition to that now authorized, for the construction of and equipping of a courthouse in said county. To pay said indebtedness, and interest thereon, Lawrence county may levy and collect an annual tax on all property situated therein at a rate not in excess of 3 mills. The indebtedness, the bonds and the tax authorized hereby shall be in addition to those authorized prior to the adoption of this amendment. But no such additional indebtedness shall be incurred, no such bonds shall be issued and no such tax shall be levied until the estimated cost of the construction and equipping of said courthouse hereby proposed to be built, its time of completion, and the amount of the increased indebtedness, the rate of interest to be paid thereon, and the period over which the bonds to be issued will be refunded, shall have been determined upon and made public by the county governing body of said county; and the proposed increase in indebtedness and the issuance of bonds and the increase in rate of taxation first shall have been authorized by a majority of the qualified electors of said county voting upon such proposal at an election to be called by said county governing body for said purposes to be held not less than sixty (60) nor more than (120) one hundred twenty days after the adoption of this amendment.