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?
You're right. If you have a good paying job then one should not left it for crypto especially if you already have a family that needs your support as earnings from crypto is not stable so you wouldn't want to risk not having any income as you are still unsure if you can earn from it. At least if you have a job then you will be able to provide for your family's needs and you are sure that you can still receive something.
I think your job should keep running, even though the salary of your work is not much but it can be a stable finance rather than a job in crypto, I do not advise to leave work because it's a bad idea and will only reduce income.
The ideal way would be to make it as an extra income than a main source of income. There is a possibility that you can earn much bigger income from crypto than your job but there is still a higher possibility of not getting anything from it so better be assured of having a fixed source of income. One has also a choice of practicing trading until such time he becomes profitable so that he will have a choice of leaving his job if he wants to but it may take years to do it.