Hi, and welcome to the Forum! Do you have any idea what species of tortoise he'd be interested in? If you don't have any experience with tortoises, Russians are a good first tortoise (Testudo horsefieldii) But one thing to keep in mind is that, even though they are a small species, they still need a lot of space to wander. So while he's indoors, a large plastic tub with a large floor space would make a good enclosure for him. Then once good weather comes around, you can set him up outside in a safe outdoor enclosure.
We have plenty of ideas for enclosures in our enclosure section.