You didn't even mention the price they're asking?
If you get to extensive in your examination of them, and then decide to buy, you may also re-enforced the in the sellers mind they are "sellable" (desirable).
You might want to only attempt to see if they turn over using the clutch. Not turning over would be a bargaining tool on your end. If they aren't overly rusty, getting them road ready should be rather easy.