So be ready for costs. Besides what everyone knows.....that if a buyer complains, they win and get their money back and get to keep your thing, if paypal is involved, expect a 1099 k and then you'll need to document everything if you don't want to pay all taxes on the sale price total you've raked in (including paying tax on the amount you spent for shipping).
A couple years ago, my son sold a bunch of old Legos to help while looking for a summer job. Being the research geek he is, he found lots of $20 figurines and rare pieces to kits that people wanted. Did you know every single lego piece is numbered and you can find every kit that piece was used in? Anyways, he raked in thousands of dollars. Come tax time, he got the dreaded 1099 k which documented every month's payments he took in. With tax accountant help, he did fine, but that cost him $300 to sort out.
If you're selling by craigslist with cash, you won't run into these problems, but good luck on eBay.