I took on an oldie a couple of months ago. Different situation as he was in a paddock with people doing their best to look after him without having any knowledge about how to do so, so obviously I had to fork out a bit in the beginning to get him wormed, vaccinated, feet done, etc etc.
But, I think where I was originally headed was to say if you know he really will boost your confidence again he could be a great asset. Kody (my old boy) will be the horse I teach my partner to ride on as he is so laid back, very much a been there, done that kinda horse. Chances are that this appy could be the same.
However, you do have to weigh up the extras that come along with owning an older horse. If he has arthritis you're probably going to want him on a joint supplement as well as some variety of "senior" feed. He may need his teeth done, depending of course on whether they've been done recently. Basically, there is a whole host of things that can sneak up on you when you have an older horse.
But again I say, If you are prepared for all the 'extras' then I say go for it, especially if he could turn out to be what you need to get you back in to the swing of things