Well done!
I do this for a fun side hustle. It certainly doesn't make enough money to replace a job, but I love looking through books, so it's a win-win for me. I picked up ten or so books this weekend from various Goodwills and the ones that will sell online will sell for enough to make up for what I spent on the ones that I just want to read. And when I'm done reading them, the ones I don't want to keep will head off to their new homes at Half-Price Books.
Of course, after doing this for a few years, I have about a hundred books in the to-read pile...