Hey! As a senior in college that will be graduating in the next month there is 3 options that i would consider the best.
Chegg.com (which is a great resource not only for books, but also questions on homework/quizzes ect)
I have typically rented books on Amazon for the last 5 semesters or so. They usually have the best prices around. Chegg is also a great place to rent books as well and is very student friendly. eBay you can get books surprisingly cheap (because students no longer need books after they buy them for the semester and will sell them on eBay to get some quick cash, so if you look at the right times, before/after semesters start, you might get a good deal)
I would strongly advice against purchasing/owning books. You rarely will open them up after your semester ends. Always rent if able, But at the same time sometimes professors will make you get like secondary smaller books in addition to the regular book for the class. Sometimes it may be cheaper to buy it on amazon than rent it elsewhere, so just do your research on various sites. Hope this helps, good luck in school!
As a graduated Nurse from college I found it very good to rent general books. Amazon.com is very reasonable with rentals and the purchase of used books if that is the route you want to take as well as selling them. They are easy to work with in reselling your books. I did purchase some good used pathophysiology books to keep because in the medical field you will continue to use them during the semesters. All of my book hunting was on Amazon so it draws a lot of students. Good luck with college and God bless!