Depends on how capable you are in gettting knowledge and transfe

Capable people buy old cars - not only to find the best deals but to learn something in practices.

You learn alot while trying to solve a problem: search, get the information, get the necessary parts and tools, learn to follow instruction and invent your own fix solutions. You will even know your cars better than ASE certified mechanics. 

When you accumulate your experience, you will know why some people likes to buying old cars.

It is rather than get a deal, but a hobby. Imagining you get a 72 Mercedes Benz for $2000 and restore it to showroom condition; imgining you get a late 90's Jaguar with $1500 which is not drivable due to leaking power steeering pressure hose (whcih cost $120 and 1 hour work), and fix it then enjoy the classical stylish road drive. 

For buying old cars, there is some personal experiences:

Not buying Japanese cars - they were designed to be abused; no one can detemine the actual quality left for you.

Buying lexury cars - You get more than you paid. European lexury cars need good care, so you probably get a nice one if it has only one owner; if more than one onwer, better not to touch it.

Buying at auctions. Car are not so bad in auctions.