In Dragon Ball, in addition to fighting to protect the Earth, Goku and the other Z warriors still have to do normal jobs to earn money to feed their families.
As we know, from a young age, Gohan was forced by Chi Chi’s mother to pay attention to his studies.
However, we also know this is a field that does not have high salaries in any universe.
At one point Gohan was offered a job as an assistant professor but he ultimately turned it down because it would take too much time to spend with his family.
So certainly the amount of money Gohan earns is not enough for Gohan to financially support his family.
As we have seen Goku struggled to maintain his life as a radish farmer under Chi Chi’s orders.