Where can I get a good deal on health science text books?

I probably should have asked this question a long time ago but….

I’m in grad school for occupational therapy and books are quite expensive (as expected). In undergrad I generally tried to get away with not having the books or holding off to buy them but the same books keep coming back to haunt me! Now that I’m in grad school and now that my classes keep requiring the same books I would like to actually buy them however I cringe at paying anything over $65—$85 for a book (I’m the student who throughout college has had to buy books paycheck to paycheck)

Does anyone of any websites or tips to buy books (more specifically therapy or health science books) or have any books for cheaper. I do know that any college, health science, and/or significantly important book is going to be pricey but I’m trying all my options. I generally have used bigwords to compare books and I’m not interested in renting books. I have talked to my professors about possibly getting a less recent edition or even the international edition however certain professors aren’t too pleased with that so it would be a sticky situation.

Thank you so much!!