Hi Dothedealnow
I'd say visit as many homes as you can, even the ones that for some reason you might reject on initial impressions - the more you have to compare the better
maybe visit the first time after a phone call, just to see how the manager deals with your call - then definitely visit again unannounced at a different time of day
keep your eyes and ears open - how do the staff interact with the residents? - try to have some time to just sit in a lounge to watch what happens around - check cleanliness, of the home and the residents - but don't be fooled by shiny new stuff - a bit worn in but cared for may well be comfortable - ask any question that pops into your head and listen to how they are answered as well as the words used, don't fall for 'patter' - think of something your mum may do that is challenging and ask how this will be handled - check visiting 'times', in my opinion there should be none, you should be free to visit whenever as this is will be your mum's home - use all your senses; a good home will deal with 'accidents' efficiently and kindly, so there may be a note in the air but there shouldn't any lingering 'old' smell - if a garden is important to you, check it is accessible to residents - if activities, ask what and when - is the room big enough to not feel cramped and what are the showering/washing facilities like
I found that I had more idea what I was looking for after I'd looked at a couple of homes because I began to realise what questions I needed to ask and what their answers should and shouldn't be
nowhere will be perfect, it's like buying a house, you discover which compromises you are willing to make and what you must have in place
all research done - go on gut instinct (eg I rejected an all singing, all dancing home which was lovely, I had no criticism of it except that I didn't feel my dad needed the all singing and dancing; I was right he needs calm and quiet and the staff in his home quickly realised that and saw that he had some social time but also time in his room on his own)
good luck with your search
PS ask what they will do when her money runs out! (even if you think it won't)