This is defiantly an area I'm interested in. However, I find that the barrier for entry is pretty challenging. IE, finding the right product. The other aspects are well within my skill set.
It's easiest if you can leverage knowledge you already have. I also tried stores selling items I knew very little about, and it was much harder. =)
There are many tools for finding what's selling though. The best ones are paid, like Terapeak (http://www.terapeak.com/), but you can also search eBay completed listings and get a sense for what's selling.
Finding the right product(s) is definitely the hardest part, though -- you're absolutely correct. Not only is it hard to find products, you also have to find products with margins that enable you to make money. For some of my sales, I only make about $1-2 dollars. Which is something I need to improve, for my own business.