The college's library should have all of the text books.
Some of them are on a special shelf, where they can't leave the library, some you can just check out. DH always checked there first. He was able to check out 80% of his text books every semester.
THEN.. see which edition the professor is using. Go to
amazon, and buy an older edition. DH spent $3 on some of his books this way. The page numbers will not be the same, and it takes a *bit* of effort to correspond with the professor's notes. But not much. His professors always had no problem at all with this.