Instead, encourage him to invest according to his ability, and gradually increase his stake. He will be able to grow with the profit money, not by borrowing. The right advice from a friend is the most significant help. If you can do this, I think it will be the best.
High volatility don't mainly fit into taking loans, due to the risk, sometimes it can be worthwhile on the long term, but nobody would allow a loan that much grace period. For a debt that'll require fast pay back within a short time, Op's friend should be better off investing little by little his own income. He's trying to be fast and wants high profits, yet, he's to slow down not to encourage greed, and accumulating losses or regret.