Selling on eBay is definitely not ‘passive income.‘ My wife and I had a store for several years. We had a friend whose brother lived in Turkey and was able to buy huge amounts of trinkets (jewelry, bracelets, etc.) at wholesale from a Turkish factory, ship it to us and then we’d resell it at a fairly large markup (our price $1, sell for $7 for example).
It was a good deal at first, and some of the items – surprisingly things like religious icons – sold very well. But it was a HUGE amount of work to deal with the posting, packing, shipping, dealing with “special orders” and so on. We tracked time spent on it for a while and finally realized – after our Turkish connection got greedy after seeing our resale prices and raised his – we were making pennies per hour, especially considering eBay’s never-ending price hikes.
Unless you can sell a very small variety of inventory (i.e. eliminating the need to take photos and write up new descriptions) and you can get the items with a minimal amount of effort or get items that have fantastic mark-up potential, I don’t think you can make much selling online. My uncle (who unknowingly is a “retired” ERE guy) goes around to yardsales and identifies items people have that he KNOWS are rare, or valuable but the sellers don’t. He sells them on eBay with huge markups, so it’s worth it for him. But he’s spent years and years perfecting his knowledge of kitschy valuables (like in Antique Roadshow).
I’ll tell you how to make some money selling on the internet - write and aggressively sell an ebook (pdf or whatever) called “How to Make Money on the Internet.” Lifestyle design bloggers are all about this – they’ll sell you a book and tell you it’s the way to get your life right-sized. Those bloggers create a single product and then resell it endlessly. That’s the only product that I personally ever would sell on the internet as a way of making income again (rather than just disposing of something I don’t need but wanting to make some money off the disposal). I say this cynically – you can, of course, sell meaningful and helpful ebooks, but you are, in the end, selling it to make money for yourself.