Code Sections 44-7-31, 44-7-32, 44-7-33, and 44-7-35 shall not apply to rental units which are owned by a natural person if such natural person, his or her spouse, and his or her minor children collectively own ten or fewer rental units; provided, however, that this exemption does not apply to units for which management, including rent collection, is performed by third persons, natural or otherwise, for a fee.