End-of-season sale extractor — how do I check a secondhand one isn't a rust bucket before I hand over cash?

Texas, fourth year, fourteen hives, and I'm finally done borrowing my club's extractor. There are two secondhand ones for sale locally at the end-of-season price and I'm going to look at both this weekend. I've never bought a piece of equipment like this and I'd rather have a checklist than an opinion formed in someone's barn. The two on offer: a nine-frame radial, motorised, about fifteen years old, from a beekeeper scaling down; and a four-frame tangential, hand-cranked, age unknown, from an estate sale. What I think I should be checking. That it's food-grade stainless throughout and not painted steel, which the older tangential might be. The bottom of the drum for rust and pitting, especially around the gate. The gate and its threads. The shaft and bearings — any play, any noise when spun by hand. What I don't know: whether cage damage matters much, how to tell if a drum has been distorted, whether a fifteen-year-old motor is a liability, and whether a hand-cranked four-frame is actually enough for fourteen hives or whether I'll regret it in the second box.