As stated look at the blades but pay attention to other details than just rust/clean/chips. Look at the spine to see if there is hone wear, is it even, excessive in some areas? Does the blade have a smile/frown? Does the bevel look even or are there wide areas? Is bevel even on both sides? These can make the difference in a blade being worth 10.00 or 100.00.

I am no expert by any means but I have waisted a few dollars on some junk blades to learn these lessons