If they have a library then they probably made the books or scrolls themselves, which would require at least a scriptorium and possibly a herd of cows for vellum. Depending on the monastic tradition they might a small industry, like wine-making, which they can use to trade for things they need occasionally and don't have access to. They probably also need a place to meditate and ponder the ineffable, so a serene garden or a labyrinth to walk, a cloister to stroll, or some other mode(s) of entering a meditative state.

Or maybe they do that by farming!

cheers,
Meshon