No discount, except as provided by the Eastern Sandoval County Arroyo Flood Control Act, or commission shall be allowed or paid on or for any security sale to any purchaser or bidder, directly or indirectly, but nothing contained in that act shall be construed as prohibiting the board from employing legal, fiscal, engineering and other expert services in connection with any project or facilities authorized in that act and with the authorization, issuance and sale of securities.