I sell ebooks [0] and currently they are my only source of income (if you don't count savings interest). I started writing books as a last-ditch effort in late 2018. Had left my job in 2014, was living on savings and the occasional workshops I conducted in colleges. I had plenty of material prepared for workshops, so I started converting them to books.
First book didn't sell much but initial sales of the second one got me enough to cover about 2 months of expenses. Combined with workshops, books helped me through 2019 and early 2020. (Note that I live alone, in outskirts of a city in India - my monthly living expenses is around $150, which includes rent and domestic help)
Pandemic meant I didn't get workshops anymore, but fortunately, my ebooks sale picked up enough to more than cover that loss. I even spent about 5 months to just update my earlier books. Currently working on 9th book that I hope to publish by end of this month.