Protip:

Find an enthusiast forum for that specific car

The next intelligent question you want to answer is, "What maintenance will likely need to be done?" You want to ask the owner this, and also the enthusiast forum for that specific model; seriously, most cars have a forum dedicated specifically to that specific model, like this one for the Ford Taurus. Google is your friend here.

The maintenance could make the difference between a cheap used car and an expensive one. 

I chose an image of a Pinto above to drive home an even more salient point:  is the car safe?

Safety really should be the number one concern. 

It doesn't matter how safe the car is if maintenance means that you can't afford to keep it running.

You're right. Both safety and maintenance cost are important.