When any railroad shall be opened for use, the General Assembly may, from time to time, alter or reduce the rates of toll, fare, freights, or other profits upon the road. However, the rates shall not be so reduced without the consent of the corporation as to produce, with the profits, less than fifteen percent (15%) per annum on the capital actually paid in or, unless upon examination of the amounts received and expended to be made by him or her, the Secretary of State shall ascertain that the net income derived by the company from all sources for the year then last past shall have exceeded an annual income of fifteen percent (15%) upon the capital of the corporation actually paid in.