You can earn decent money by selling books (on your website and platforms like Amazon). Piece of advice – never limit yourself to one platform only. By posting books on your blog or website you’ll earn most of the cash since no one is taking the fees, and by publishing on platforms you get exposure.
NOTE – You’ll want to have an SSL on your website/blog if you wish to sell there, you don’t want to risk peoples’ info to fall in the wrong hands. How to know if you have SSL? If you see a little lock next to your URL in Google, you’re good to go.