I know that It is part of the joke, but They are "mafia mini bosses" with many underlings but don't have any money ... So the Mc is living at a barrack, eating almost trash, even though having a really wealthy aunty (Probably the whole Mother branch) whose is giving "him" a "proper" living expense (That almost always include something like the schools fees).
.. And his parents aren't not embezzling his wealth... hmm ok.If It were a realistic manwa, this manga would be pretty dark.