The most important decision you make, and the one with the permanent consequences, is which pattern you decide to buy. Look closely in eBay antiques/Silver/Sterling/Flatware at the categories for each manufacturer. If there is a collection for sale, search for other listings that use this pattern name to get some idea of how common this pattern is on eBay.
Sometimes you will find sellers listing collections without a pattern name, though that is getting less common over the last several years. Most sellers, even if it is their first time on eBay, realize that they will get a higher price if they do a little research on any of the many pattern identification websites so they can post the actual name of the pattern in the title of the listing.
Most sterling silver flatware will show some signs of use, but silver can be easily polished using a silver cream, and unless an item is seriously abused, flatware pieces will quickly and easily polish up so that you will be proud to have them on your table. Be very careful of black pitting on stainless steel knife blades, as this does not remove easily (or at all), and items with these marks should be avoided if at all possible.
Some sterling silver pieces may require a bit more elbow grease (that means more vigorous and longer polishing) than others, particularly the bowls of serving spoons for example, but generally there is little to worry about with any listing that gives a full description and provides good quality close-up photos. Another thing that can happen is the blades of knives can come loose from the sterling handles, but this is quite rare in my experience and any seller that doesn't acknowledge even the slightest wobble whatsoever in a listing is far over the line into misrepresentation and refund time.
The Sterling Silver Flatware is an online store with hundreds of different Sterling Silver Flatware at discounted price.
