I ever heard that people choose to quit their job for doing some crypto job. Whether it is trading, mining, or bounty. But I think that's the worst idea. Maybe they think that kind job like that can earn many profit but they doesn't looking at the risk and keep do it. Look at the market, they stay red and it will hard to get profit from investing or trading. GPU price is more expensive as well as a lot of capital to be spent when starting mining. Also Bounty Hunter has bad condition right now with too many SCAM ICO which caused some of them just wasted their time and doesn't earn anything.
How they can earn money for daily need if only depends on the crypto?
Indeed, and it will never be. Once bitcoin disappear it would be tough for them to live because their income comes from only one source and that is to earn crypto especially when they don't have enough savings for some future purposes. Also, it is not good because bitcoin price fluctuates thus, their income would change either positively and negatively. Sacrificing your own job just for the sake of earning crypto is a worst idea of all.