If you want the least amount of risk with potentially 20% gain, I'd go with bitcoins. or maybe some Ripples
Investing that dollars in bitcoin is much better and not 20% but he will earn a large amount of profit if he do not spend them early and hold them for longer time at least for 1 year.
I think the bitcoin is a good investment for the long time. That has been proved in the past 6 years.