Without any photos, it is not easy for anyone to judge the value of this tractor. Condition is important. Does the engine smoke? If so, when does it smoke and what is the colour of that smoke?
What condition is the seat in? How much free play is there in the steering? How does it drive? What kind of cut does the deck give? Is the deck noisy? How does the deck clutch feel when you engage it? You should have to push strongly at first and then the lever should pop-over into the engaged position.
Personally, I'm with Gary.. I think that the asking price is high and $400.00 is more in tune with what these normally sell for unless they are in exceptional shape.
Parts are not a problem for them. A Kohler K will be noisier than a modern engine but the K will out perform the modern engine.