Very hard for BTC to become a source of income mainly because of it's variety and lack of stability and therefore you can't get it stably, and hence can't depend on it as a source of income overall.. Those working for BTC companies or doing translation professionally can probably depend on it as a source of income.
I have seen lots of crypto traders making thousands of dollar every week or even more which I think will be enough for anyone to have quite moderate lifestyle. But nobody can earn enough bitcoin for free or without doing anything to be able live just with those free bitcoins.