No matter how much investment your friend can afford in Bitcoin. It can be beneficial for everybody with almost any savings. But the one important thing that matters is that what knowledge your friend has about the crypto-market, its behavior, how much time he can dedicate to learn how to trade and invest right in this market. As you say, he has a big family and a hard main job, so I think he won't be able to get involved in this market as a man should be. Because he wouldn't have time for that. People that have no knowledge about the crypto-market should stay out of it because it'll "squeeze" them like a Bulldozer and they will lose all of their money. But even if he makes a good profit once, a person in debts will decide to take even more credits and loans expecting to make even more profit to cover his debts. And that is when the market will punish him and leave him empty-handed.