I'm sorry my friend. The odds would be seriously stacked against you. These fish are known starvers and will if not acclimated to prepared foods will refuse to eat even if food is hitting them in the head. If you are dead set on getting the fish I would read up on how to train them and I believe there are also some YouTube videos to watch as well. Go get yourself some live pods to help with the training and try to trainoff the bat. Your tank will not be able to sustain him.
BEFORE you consider that ask the pet shop how long they have had him and how long it has been since he has eaten. Are the feeding him live pods? Or has he not eaten anything for a few days. Unfortunately once this fish goes off eating at a certain point they just won't start again. So if his stomach is already sunken in, he might already have a dismal prognosis.