The Act is based on residency and not ownership. That means a son or daughter under the age of 55 can buy a home and let their parents 55 or older live in the home. A young investor can buy a home, but he or she can only rent to a 55-plus renter.
There is also an 80/20 percent rule in the Act. It is an exemption that applies if a resident who was 55 or older dies. If the spouse is not 55 years old, she/he can remain in the unit and they would fall under the 20 percent that do not qualify. The same would be true if the property is transferred as an estate to an adult child younger than 55; they can move into the home as long as they do not have children younger than 18.
One other requirement in Florida is that the board must file every two years with the Florida Commission on Human Relations. Failure to do so will disallow the community to restrict residency.
I am not a real estate attorney and all legal advice or interpretation should be done by a FL licensed attorney. ;)