I am in a dilemma. Please help!!!!?

Get more information about his supposed "business". Ask him what his business plan is, what he plans to market, how much he plans to charge, how much he plans to profit, etc. If you're going to contribute to his capital, you need to know everything about what it's paying for. If I were you, I'd be very skeptical. It's also not just a matter of whether or not the business is real. You need to make sure that the business is practical enough to fund and that your father-in-law is competent enough to run it.