I've been listing stuff on ebay for close to a year now full time. The hardest part, for me, is the slow periods when there is no sales. I sell almost exclusively out of my ebay store at retail prices which is part of the reason. But at other times, my prices are right and I find a buyer.
Another scary thing as a seller is the potential "sale gone bad". I've been a longtime buyer for 8+ years and have seen great to horrible sellers in my time. The main concern isn't with scammers, but with delivery of the item as I have no control on that part.
Current objective is to do $3,000 in sales on a monthly basis to become a SILVER Power Seller! I'm hoverong at around $2,400 right now, but business for March has been on the slower side.