Most of the adult neighborhoods do allow an adult child as long as a parent meets the community guidelines. However with that said the only way is to check the community itself as some have unique guidelines.
I know a Realtor in Casa Grande that knows those communities really well and could answer the questions for you if you would like?
Arizona Homes for Sale by a Guy from Iowa
I live in Arizona City and have sold several homes in over 55 communities in Casa Grande.
Fair Housing Laws provide that a certain percentage of residents in 55+ communites must
be allowed to reside there that are over 40 yrs old. When a customer calls on a listing
in these communities, we, as realtors, cannot state that no one under 55 may reside in them.
or be subject to a $10,000 fine.
Better Homes Realty AZ
Lynn911 Dallas Realtor & Consultant, Loan Officer, Credit Repair Advisor
The Michael Group - Dallas Business Journal Top Ranked Realtors