If properly maintained, they are quite reliable, though gas-guzzlers. The problem is that you're trying to take that generalization and apply it to a specific example.

See if the seller will let you take it for a longer test drive (you buy the gas of course).

Once it's warmed up, accelerate briskly (no tire squealing) from a dead stop a couple of times, listen for any noises from the suspension and driveline. Stop rather hard (no lockup) a couple of times, come to a complete stop and hold the brake pedal, same thing, listen for noises (and of course observe any odd behavior).

Find some railroad tracks and drive over them a few times. Does the steering wheel jump out of your hand? Suspension bouncing all over? Van tracking weirdly?

Pop the engine cover latches and move the cover back a bit so you can hear things. Take it onto the freeway and from 45 or so floor it a few times. Listen closely to the engine and watch the mirror for any smoke. At about 40, drop it into 2nd gear (assuming it's an automatic) and watch for smoke, keep listening to the engine.

Park it somewhere and leave it running, look under for any leaks. Go get the gas you used up plus a little to be nice. Refit the engine cover and go back. When you return, check the AT fluid (color/smell/clarity) and the engine oil (water, primarily).

If it passes all of that, it will last you more than a week, after which you can decide whether to resell it or keep it as a backup, just in case.