I use to sell books on Ebay, first editions and out of print hard to find books. This was before the yard sellers and thrift stores got smart and checked Ebay for the going price. I would buy the book for a $1 or two and sale it for hundreds. My best sale was over $800 for a book I bought at a yard sale in excellent condition for .25. I don't do it anymore, it's too much work to keep track and I don't need or want a job. The rare books are harder to find but I still keep my eye out when I go to estate sales and thrift shops. I give the books I find to a group that resells for the children's hospital here.