Subject to prior approval of the Commissioner, an insurer may acquire and hold real property for recreation, hospitalization, convalescence, and retirement purposes of its employees. All investments under this Code section shall not exceed 5 percent of the insurer's surplus; or, if a mutual or reciprocal insurer, all of those investments shall not exceed 5 percent of the insurer's surplus in excess of the surplus required to be maintained under this title for its authority to transact insurance.