Sorry, but these are questions you should ask before you buy a fish.
Anyhow, he may never eat, many of them don't. Even when they do eat they almost always starve or mysteriously die within a year.
Try things like fresh shellfish. Fresh clams still in the shell can entice them to eat sometimes. Mysis is a good choice if he'll eat it as are prepared foods for Angelfish that contain sponge. You'll also want to include some greens in his diet and you could try nori and spirulina flakes. If he does start eating prepared foods just give him a varied diet and maybe you'll get lucky and be able to keep him alive for a while.