There is a big risk involved, and besides, even though your friend is good at trading, we really don't know what's going to happen in the future, so it still 50/50, depending on your risk appetite.
In trading, there is no invulnerable when it comes to risks, there is always a risk, that's why it requires a skill in order for you to succeed and win in trading. Making strategies based on the speculations and prediction will be helpful for you to minimize the risk of losing your money than getting huge amount of profits.
I know someone who borrowed money from a bank to buy Bitcoin in December 2018, when the price is around $3000.
Right now we can say that it was a bold move, he just hold on it and I think did sold some around June 2019 when the price hit $13000 and repaid the loan. Well that is one success story, but what if the market goes down up to this point?
That's the reason why you should seize any opportunity that you can grab as much as possible so that you will have no regrets and you will not miss the chance to grow and improve your trading skill and quality.
He's lucky enough because he have great skills so that he can paid his loan using his profit. That's a good strategy and yet very risky, because what if there's a circumstances that he panicked when the market goes down and he lose all his money. If that happens, maybe that's the time where he is doomed by the market, probably his life will become miserable as he loses the money that he only borrowed in the bank.