Buying textbooks

When you were studying before especially when you were in college did you buy all the textbooks that your teacher required for you to have?I remember,I bought some of the books and the other were borrowed or I just photocopied the books that I borrowed in the library.Sometimes some of the books are not available at the bookstores.Good thing today,people can buy books on the net and deliver it to their home.

The other day,I was asked by my sister if I can lend some of my mathematics textbooks such as Algebra and Calculus to our neighbour's son.I told her that they can borrow my books as long as they gonna take care of it.It's better that someone can re-use it rather than keeping it in the shelve earning some dusts.