Your post is not clear. It seems like your "friend" wants you to give them $100k and they will invest it for you. Is that right? My first thought is that your "friend" is not really a friend, and they are trying to take advantage of you.
Also not clear. You will get 20% of what?
If your "friend" says the return on your investment will be 20%, then you really need to understand how your "friend" came up with that number. Also, you need to determine the risk of the investment and whether or not your "friend" can truly deliver that return.
If your "friend" says that you will get 20% of the profit from the investment (and your "friend" gets 80%), then that is a bad deal for you. You take most of the risk and your "friend" gets most of the reward.