The inspection report is apparently the advert I already read

They've replied that the previous owner checked it before removal, not the dealer, and there's no sheet in the sale file

Get the labels and a complete included-equipment list before travelling. Otherwise you may inspect an arm and discover the controller in the photo costs extra.

I'd consider a paid inspection if the complete price still works. Missing paperwork doesn't necessarily make the equipment worthless, but it does put a cost on finding out what you're buying.

It also makes inspected a fairly cheeky description.

Agreed. I wouldn't pay for that assurance. I might pay an independent person for a real assessment, provided the seller allows access and the total still makes sense.

They'll allow an inspector, apparently, but can't show operation because it's disconnected in storage; I've asked our service contact what they could reasonably assess there before we pay travel costs

Ask about arranging a suitable test somewhere else as part of the sale. A visual inspection in a warehouse could leave the expensive questions untouched.

Did your service contact think the visit was worth doing?

Only as an initial condition check, with operational assessment still needed afterwards; thanks, Ella Allen, for making me price the uncertainty instead of just arguing about their wording, though the numbers aren't so attractive now

That would be enough for me to pause, unless the seller changes the price or testing arrangements. You haven't wasted a bargain by finding the rest of its cost.