I have one even better.
If your college has Easy Borrow (where they can borrow books from other college libraries) borrow them and return at the end of the semester!! I do this and haven't had to buy a book for a few semesters.
ETA: Easy Borrow (or whatever your college might call it) normally takes a few days (at my college they say 2-5 days until they receive them. Don't stress!! You can always get by for a few days without a book. If you HAD to, you could always just go to the bookstore and read it there.
Also, if Easy Borrow has a different version than what your professor uses, ask if its okay to use a previous edition. Most of the time they only changed 2 sentences in the entire book.