I can not say that bitcoin is the main source of income because bitcoin is unpredictable or not stable its price but Bitcoin is one of my source of income for getting extra money.
I cannot say that bitcoin is my source of income especially that i am employed because if i want it to be my main source of income I need to give my full time to focus it . Thus, i cannot afford to gumble bitcoin and give up my career. So, bitcoin for me is just another source of income.