A person can't persuade another to do something when they have not yet seen the results for example, you as a child you depend on your parents for every of your up keep and at the end of the day you go telling them that you have an investment you want to introduce to them, and knowing how our African parents can be smart with questions especially when it comes to an online business that involves money it will be a waste of energy trying to persuade them when they haven't seen the good news in you but when u stop depending on them and pay ur bills they will be wondering what's going on they will want to know what you do from there u fit run enter them and they will be eager to listen.
So the only way to persuade a person to something is when u are the example of ur words.
Seeing is believing that what people want, I agree with wetin you say because you no go dey under your parents care and the same time you go persuade them on something wet go bring money, they no fit believe you because say they dey do everything for you, but as OP talk am wen you don dey benefit from that thing and the thing they show for your body then dey go like listen to you because you be example of that thing. The only advice wey I go give this person be say make him go find more knowledge about crypto and make e dey try go am with small small money wen em they get before him go call other closest people.