MPC: Build-It + Retring Boomers Might Buy It > A Seller's Market

Where To Retire Magazine has published what they call "The Short List" for Retirement Re-Location.
The selected master-planned communities included in the list were chosen based on first-person testimonials.

If you can believe that "first-person testimonials" are in any way reliable and objective and unbiased, then the list is exactly what you need. Here's the source:
https://www.wheretoretire.com/50Best.cfm 
The East Coast states of North Carolina, Florida, South Carolina and Georgia