some red flag:

1. if you're making 600% annualized you don't take outside investors, you prop trade for your own account.

2. He's very young and didn't have any trading pedigree: normally you would expect someone like this to be ex-js/citsec/etc

3. Sometimes lavish life style can be a give away: often the real rain makers are pretty frugal.

4. Related to 2, but if you're gonna take outside investors for some reason and you're printing like that, you sure as hell aren't gonna take it from random individual. You would raise money from one or a couple big firms or possibly a ultra hnw individual.