Step-by-step explanation:
From the impression of your friend, we can easily acknowledge that it is not something legal, which means your friend's actions basically is illegal. However, first off, if you agree to invest 500 dollars for him, you should not accept; instead, decline. Why? It is so obvious! You don't even know what he's actually going to do! We must remember consequences will always come back to us. Since it's illegal, you may be punished in the future. So to conclude, we should decline his offer.