It is true that some teachers forget the cost of books and go overboard on their reading lists. If you have a course that specifies five or six books, it's fair to ask which are required and which are optional. You won't run into that situation for a couple of years though. As a freshman, you are far more likely to get a one-book reading list.
In our course, that one book, A Writer's Reference, is the sort of thing you would keep for years because it is, well, a reference. If you ever need to do any writing after our course, you will want this book.
True story: At a recent faculty seminar, the head of the nursing department commented that correct APA citation format normally counts for 30% of the grade in nursing papers. You don't know what APA format is? That's why you bought the reference book.I guess it is possible for you and a roommate to share a textbook if you are taking the same course/section, but you will really need to coordinate your reading schedules. If both of you are last-minute readers, the next obvious question is which one of you will get the book. If one of you likes to take the book to the library to make writing easier, the other must tag along too.