Such tax shall be collected in the same manner as other taxes, and the money so raised shall be expended, and said soldiers’ memorial and monument constructed, in the same manner as is now provided by law for the construction of public buildings and paying therefor by the board of county commissioners, and the grand army of the republic and its auxiliaries of such county shall have charge of the building of such soldiers’ memorial and monument within such county. No part of such money shall be paid for salaries nor for any other purpose than that above specified.