Hi there!
You can find used copies of the SAS Certification Prep Guides on Amazon here and here. The e-book versions may be a good option. The Third Edition is the latest for the Base Prep Guide and the Fourth Edition is the latest for the Advanced Prep Guide, you'll want the most current versions!
Also, the SAS Programming 1: Essentials training course that is recommended for the Base certification is available at no cost in e-Learning format.
Additionally, you can find free tutorials here
Sample questions here as well.
I hope this helps! Good luck!