1. Anybody can make money off eBay for the most part. But you have to have a plan. Just putting up items and spending a lot of money on listing fees is not the way to go. You have to find items that will sell which leads into myth 2.
2. Not everything sells on eBay. Items where you can ship cheaply tend to sell much easier. Unless you are getting a big discount who wants to spend hundreds of dollars on shipping a TV or furniture when it would be about the same even with the discount if they go around the corner and get it for about the same price. It's also harder to find margins on items such as clothes.
3. You have to be thrifty. Don't spend $50 to sell a $10 item. It's fine if you are doing it to increase attention on bigger profit margin items from time to time.
4. Don't quit your job yet. It takes time to learn what to do.