424.13  Income debenture certificates; exchange for stock.--The articles of incorporation may authorize the issuance of income debenture certificates bearing no greater interest than 7.5 percent per year. After the incorporation of a limited dividend housing company, the directors thereof may, with the consent of two-thirds of the holders of any preferred stock that may be issued and outstanding, offer to the stockholders of the company the privilege of exchanging their preferred and common stock in such quantities and at such times as may be approved by the Department of Community Affairs for such income debenture certificates, the face value of which shall not exceed the par value of the stock exchanged therefor.