I've perused our local GoodWill stores and they often have decent usable texts of various grade levels available for a few bucks each although, these thrift stores are becoming a little bit proud of what they sell. Also, local libraries might have an annual event where they sell older tomes to obtain funds to replace them with newer books. Check your local library, ours does this every year.

Flea markets and yard sales - the best!

I have been considering trying to 'build' a reference library for my young son and grandson. I have this uneasyness about the future of our 'digital age' and have started collecting hard copy books. I'd like to build a basic 4-12 grade core subject library, just in case I have to teach my off-spring once the lights go out. Anyone have any links or know where I could pick some of these up on the cheap?