There is one further thing to mention when you purchase used textbooks. Many if not all college classes now have an online site that is associated with the textbook. Students are required to use the site as part of their class. In order to access the website, it’s necessary to have a code which is included with a new textbook purchase.
Some used books may also include this code. However, if the book doesn’t have it, or it has already been used by a previous student, you may have to purchase the code separately. This of course adds to the cost of the book purchase.
You will probably still come out ahead, even if you have to buy a new code. However, it’s something to consider and ask about when you are buying your textbooks.