If you really care about your friend better to tell him everything, and teach them how to play in the market. Im not saying that you idea is illegal, its legal as long as you are committed but again teaching him about cryptocurrency is the best thing that you can do, let him enjoy the cryptomarket.
giving an understanding of crypto is more useful than we buy for others, because an understanding and knowledge is more useful in the future, with a good understanding can make someone able to buy and sell independently.