The Housing for Older Persons Act of 1995 (HUD link below) allows an exemption for 55+ communities from the Fair Housing Act. If it weren't for this Act, then families with kids, etc., would be able to live in The Villages. Basically, it allows The Villages and other 55+ communities to legally discriminate against families when it comes to houses (families are otherwise protected under "familial status" in the Fair Housing Act).
http://www.hud.gov/offices/fheo/library/hopa_final.pdf