I think you should have someone who is pretty knowledgeable about frames before you purchase one. And someone other than the seller. There are little details that can turn into big headaches.

head tube diameter
seat tube diameter
ohhh has the steer tube been cut?
braze-on or clamp-on for the front deraillure

first three can become a major pain...

And start figuring out your component cost: brakes, deraillures, cranks, cassettes, chainring, pedals, brifters, cable guides, cables, wheels, rim strip, tube, tire, head set, stem, handle bar, tape, seat post, seat... did I get it all? and assembly costs by LBS.

It can be fun to build your own but I've done it enuf times. mehh :|