Interested in correct size frame, decent components, paint and metal finish in nice condition, extra accessories. I then check wheels to see if they are badly out of alignment and have hops. Then I look for frame damage, which I have luckily found to be rare. Then check to see if anything is seized. I don't care if the tires are dried and rotted, and tubes have holes or defective valves. I replace them. The nastier it looks with dust and grime the better, since the price will be adjusted accordingly. It doesn't matter what is on the surface, since it all gets taken apart, cleaned, regreased, replaced, etc. "Donor" bikes are a different story. Just looking for the parts and accessories I need. They are all that needs to be in top condition. Purchase prices need to be very low for me, since the time spent on overhauling and cost the for replacement parts and materials adds up quickly to the point where it isn't worth it... unless it is a really special high-end bike that I like, and it needs to be the corrrect size. If they think their rusty old "vintage" department store bike is worth a fortune I leave quickly. Otherwise, ten minutes is more than enough time for me to do a complete inspection for a purchase decision.