Framebuilders - What to look at in a Frame

All -

I might be looking at a lugged Columbus SL frame this weekend - apparently a guy in my neck of the woods used to do some framebuilding & he's selling one of them, a road frame. It is quite cheap, less than $100, and might even been in my approximate size. What are some different things I should look for that might indicate potential problems with the frame? Any suggestions?

And, Columbus SL is the a second tier/second best steel, isn't it?

Thanks for your thoughts and suggestions.

BDS

In the old days I think SL was top of the line.
Check all the contact points for damage.
BB threads in good shape ?
Head tube undamaged where the headset goes in ?
Steering tube threads good ?

It's a bit hard to check alighnment, but you can do the string test I guess.
Do wheels fit in nicely ?
Rust inside or out ?
Cracks around any joints ?

get a long wood stick, put a rag or towel on the end and shove it down to the end of the seat tube and twist. Pull it out and check for rust debri.