The permanent residents of all housing units in the senior housing development must be at least 55 years of age, except that the spouse or a member (other than a child) of the immediate family of an eligible permanent resident (or, in the alternative, a single live-in adult domestic employee, companion or nurse of an eligible permanent resident) may be a permanent resident regardless of his or her age. A maximum of one child, aged 18 or older, may also reside in any housing unit as a permanent resident with his or her parent or parents.