Hi there,
My second year "big sib" gave me all of the texts that I needed for first year complete with wonderful notes. She was awesome and I passed the stuff on to my little sib too. There are some texts that you just need to purchase because it is easier that relying on the library.
Some people used the library copies but found that pages were missing or people had highlighted them to the point that it was distracting. There were also some courses that you never wanted to purchase the text (Psychiatry) because you were never going to read it. This is were your "big sib" comes in handy.
I did purchase my Gross Anatomy text and ended up tearing out the pages as I went through the text. I used First Aid for USMLE Step I and Q-Bank so I didn't need a bunch of review books. I studied my notes and syllabi for class exams. I found that I really didn't need too much textbook reading but anything mentioned in the text, in the syllabus and in class was fair game for the exams.
The bottom line: You need to at least have access to the texts if there is assigned reading to be done. You might share a text with another student if the book is huge and you don't want the hassle of trying to get the library copy. Othewise, you may be able to buy a used book cheap and sell it once you are done. I ended up selling all of my textbooks once I was done with second year.
njbmd 🙂