Invest in a crypto market situation accordingly. There should be a framework for him to invest in which time to invest. And at what time to sell.
This is no longer a new thing here and a lot of people, if not everyone, knows that already. And most of us do it every time, we buy when the price is down and expect to sell anytime the market goes up. Thats why you see many people complaining about the price not going up cause they want to sell and make profit.