Library Course Reserves
All campuses have a “Course Reserve” option at their libraries. Faculty can put required course materials into the Course Reserves system and students can check out those materials for a limited block of time, typically three hours. Ask your professor is he/she has put a set of course materials on reserve. If not, you can try to explain that buying the books would case economic hardship and ask your professor if he/she can put a set of books on reserve.
While the library reserves are for hard copies, there is also an e-reserves system for electronic documents. Professors put articles or sections of books online in .pdf format and they can be downloaded for free.