I paid 5 hundred for my 1000, fully restored, with a fully restored 44c deck, creepy gear, 3 point, brinly sleeve hitch, headlights, rebuilt engine with 6 hrs., 36QA snow thrower, IH wheel weights, 42" snow blade, and a stack of original literature for it (sales brochures, service manuals, etc...), and some extra parts (lift rods, hr meter, etc.). Photos of it are in my profile album--it has the shiny chrome hubcaps (not original). Offer him $100.
I got very lucky on my find.....Like the others have already said, pictures are needed to see what condition it is in and what extras come with it. If the clutch needs rebuilt and iso mounts need replaced, then you can count on spending a couple hundred extra.
Cub Cadet 123