Try your local library. Normally they have sales at least once a year. You may find some of the books there for a discounted price as long as you are good with "used" books. Some libraries also sell first edition books. These may be offered to "friends" of the library before the general public though. If these are books you have not read yet I would recommend getting them cheap first. After reading then you can decide which one one you want in a first edition and look for a good copy.