Copper is right that you can find some good deals on eBay. One word of caution though; make sure you're buying from a reputable seller or a music store on eBay that guarantees the instrument. It would be a drag to buy a used instrument at a good price only to discover that it needs several hundred dollars of repair work to make it playable. If you are purchasing from an individual, they may have a beautiful instrument and not even know it's in need of a pad job.
My main suggestion to you, however, is to learn to play alto first. You'll most likely find the alto embouchure easier at first helping with pitch and control issues. Another advantage is that you can rent an alto while you learn the instrument, making you a more knowledgeable buyer later on.
Either way-soprano or alto, good luck.
Randy
jazz books
www.randyhunterjazz.com