There are a few equine developments here in TN around Big South Fork. Not necessarily retirement communities, but most full timers that live there are retired. Most properties are on the small side, between 1-5 acres, and do have their own barns or run in sheds. Some people do keep these places as vacation homes that they rent out when they are not using them. We recently looked at a couple houses there with the thoughts of selling our LQ trailer and keeping a place there to ride out of or trailer locally in that area.
There does seem seem to be a nice sense of community, which is something I miss being out on a large farm in a non-equine area. I have heard people there complain about the difficulty of getting a farrier or vet, although I am much closer to a large city and still have the same issue. Cost is another issue, as we have 70 acres with a small, but very well appointed house for about the same amount of money for the tiny acreage with large, well appointed house.
Here are a re a few examples of property in the Big South Fork developments.
http://www.realtor.com/realestateandhomes-search/Jamestown_TN
http://www.realtor.com/realestateandhomes-detail/Obey-Blevins-Rd_Jamestown_TN_38556_M71851-90735
http://www.realtor.com/realestateandhomes-detail/719-End-of-Trail-Ln_Allardt_TN_38504_M85302-84814