At one point I was going into this business, in the Northeast, so I know a few things--most of which has been posted already. Texas Guest's picture is pretty consistant with what I know--

Also, know that they are required by law to provide entertainment on a regular basis, though just how they do it is up to them, so there is always a need. There is a directory that you can find at a library, or some such place, that provides detailed information on all the nursing homes and residential facilities in the US--listed by state--and it also lists the chains--worth it's weight in gold..

One thing that I did was to walk through the facility with my uke, playing for the folks who were confined to their beds.   You don't need as many songs (though you have to be ready to improvise a verse and chorus of anything you get a request for), and you talk more than anything else, but for a few minutes, for them, you are Elvis, Frank Sinatra, and the Great Caruso, all rolled into one--and very few others do this-

Also, there are a few booking agents who handle this stuff, ask around, and you'll find them.