Ebay is a bellwether. It's been around since nearly the start of the online boom. But, like any other platform, success can seem fleeting if you don't know what you're doing. Selling items on eBay, professionally that is, can be an art form. Getting people interested in your auctions isn't always easy, especially when there's hefty competition and low demand for what you're selling.
How much will you make? I think my best month with Google AdSense was almost $5,000 over the last ten years. That amazing month blew my mind since it was actually near the beginning of my blogging journey. When you go from making zero to $5,000 in a month, that will rock your world. For me, it also got me even more excited because I knew there were other ways to monetize.