Do not forget that you need at least a computer and a digital camera. A scanner maybe good but scanning photographs is costly and time consuming, not good for a starter. Having a camera with a 640x480 resolution is good. If you've already got one, though, and would rather not buy a digital camera 'til you've explored this business of eBay selling, it's the least expensive way to go.
Why that resolution? Because a lower resolution results in low quality pictures and less likely to get bids and you don't want that for sure.Besides, few people will take a risk on something that isn't well represented in a photograph. On the other hand, a resolution higher than 640x480 may result in pictures that will take long to show up and will probably bore your prospective buyers and people won;t waste time waiting for your pictures. Remember, there are lots of competition at eBay!
The next thing you need to do is to make your eBay research. Research is an essential key to your ebay success. Research will uncover you three important things that will directly affect your eBay sales. It will give you an idea on the market availability of your desired items to sell, it's worth and the competition it has at ebay.