The said board of trustees shall have power by a majority vote to draw said pension money from the treasury of such city and invest such funds or any part thereof in the name of “Board of Trustees of the Policemen’s Pension Fund”, in interest-bearing bonds of the United States, of the state of Missouri, of any county, township or municipal corporation of the state, or for the purchase of any judgment in any court of record in this state, or loan same on real estate in the city when such pension fund is established, not, however, exceeding sixty percent of the assessed taxpaying valuation of such real estate, and all such securities shall be deposited with the treasurer, which shall be subject to the order of the board. No loans on real estate shall be made drawing less than four percent net interest and such interest shall become a part of the fund when received; provided, that no member of the board of trustees shall obtain a loan directly or indirectly from this fund.