It is not wise to leave your full time job just for trading crypto. As of now it is not stable and unpredictable. Maybe investing needs time but you should not sacrifice your job for it. Its better to keep your job, earn some money, fill in your financial needs and invest your extra money on it.
You have given the good suggestion to him because it is not good for his family. Don't completely rely on this cryptocurrency because sometimes it takes a lot of time to recover the prices, so firstly we need to take care of ourselves before leaving the JOB.