[FONT=Franklin Gothic Medium]You can usually find some fairly good deals by using Half.com or Amazon
.com Marketplace (look up the book via the ISBN, Title or Author, and they will tell you how many used are being offered by unique sellers).
[FONT=Franklin Gothic Medium]Be sure to check the feedback/reputation of sellers in each of these venues, if you do decided to order, as well as the shipping time involved. Also, while you are waiting on books to arrive via online order, check your school's library to see if they have a copy or two on reserve or available for checkout.
[FONT=Franklin Gothic Medium]Good luck!