If Bitcoin isn't legal in a country or is banned in a country then one should never accept Bitcoin payments directly from others. I would advice you to suggest your friend to not accept Bitcoin or crypto-currency dealings if they're not allowed by government. Any time if authorities get information about his shop then they might take strict actions against him. If he has invested in Bitcoin then that's not an issue he should hold that investment and if he wants to invest more in Bitcoin he can do that as well, but he should never share details about his wallet or investment details with anyone.