Actually, if at all possible I recommend that you get in more than one and go for a spin. They are rare enough to be "few and far between" and you don't want your first ride to be the one you assume is correct in all respects, especially if the condition of the car is suspect or it's a "fixer upper".
You want to be reasonably certain that that rumbly noise is tires and not wheel bearings, if it comes to it.