I do this often, and it can be very inexpensive if you build it up with vintage parts in good condition.
The easy recommendation is to go looking for big production brands of the '80s - Trek, Miyata, KHS, Centurion, Fuji, Nishiki, Lemond Bianchi, Specialized, Novara, Bridgestone. If you see an ad that sounds good, look up the model and find an oldcatalog online. They often have geometry and sizing information, plus tubing and other details.
All of those kind of bikes will be English thread and have standard derailleur hangers.
Aside from crash damage, check the input spots - dropouts, cable attachments, BB threads, etc.
Do consider full bikes. I often buy them and sell the boring group they came with on CL, keeping the wheels. This has often paid for the bike.