this is one of the big mysteries of the game, that's why i'm pretty certain it's not something that has been revealed yet. logistically speaking, it wouldn't make much sense, HOTS would be losing money instead with this deal. i think Quinn's restaurant is her own thing, not the HOTS. Maya says in the first episode something like "they offer to pay your tuition if you fit their criteria", meaning not all the HOTS get this benefit. later she says Quinn said she had a proposition for her, which might very well be being part of the menu, but i don't think this one and the free tuition go hand in hand. my theory is the money comes from someone above, probably the same one involved with the drugs, and who knows what they get in exchange from the HOTS.
either way, i'd stick with Maya all the way