I live in a 55 or older cooperative that I found out about from someone I know. I'd suggest asking around to get ideas, look at websites, and take tours.
Also consider your interests that you might have in common with others. Here we have a large property so there is lots of interest in nature and gardening. Also there are lots of owner organized things like book groups, crafts, woodworking, games, music, excursions, and so on.