My advice is a mix of the above Frame and bike purchase. Make sure the frame is in good shape (a lot of discussion above). Buy the frame you like in the right size. Find a "parts bike" that has the part you like, now you don't need to worry too much about the frame condition or size. Sourcing all the right parts can get really expensive. Sourcing a bike with the right parts on it, especially when you don't need to worry about size/condition of the frame can be really cheap. You may even need to source 2 "donor" bikes, but it will be way cheaper than sourcing individual parts.