How much rust is expected on a 16-year old truck?

I'm looking at buying a new vehicle, trading in my 2004 Ram 1500 ST (4WD, Quad cab, aftermarket wheels & stereo, 170K) on it. The rear wheel arches are rusty (one of them through, about a 5-6" long hole), and the bottom of the tailgate is rusty. Other than that there are a few scratches, but no big dents, and the interior is generally quite nice. Would that be average condition, or take it down to the rough category?