The smallest in the family, the 16GB model offers all the features of the iPhone 4S, at the lowest price.
This is a great choice for anyone who wants the latest iPhone features, but doesn't need a lot of storage space. If you're music collection is small, say around 2000 songs, and you don't have a lot of video's or photographs, in your iPhoto collection, the 16GB version is ideal.
Price wise, expect to pay between $550 - $700 for a used 16GB iPhone on eBay (check the listings below). To purchase a new version outright, Apple's price is $799. Purchasing second hand should save you around $100-$250. Apple products like the iPhone hold their value well, so don't expect a massive reduction in price. However, if you bid smart, you're bound to pickup a bargain.
Be sure to check the iPhone you're considering purchasing is in good condition, is able to take your network SIM Card (check unlocked iPhone's for sale), and is being sold by a reputable seller with a good feedback rating. Check out up to the minute listings currently available below.