Yes bitcoin has become great source of income nowadays and people are making good amount of money from it even by working part time so if they gets full time into it then it will surely maximize their earnings and they may have higher income in compare to their full time job.
yes you are right that bitcoin is a very good source of income because people are giving so much importance to bitcoin and the earning from bitcoin is also very high as compare to day jobs it is because people have seek so much opportunities in bitcoin due to which they does not need any real jobs.
Though it is not really stable unlike if you are really employed in real life because we all know that your salary is stable. Bitcoin is also good source of income if you do have a work online that pay you bitcoin that is really is. Because sometimes you dont have bitcoin sometimes you have. But as a part time job then it would be it