Billboe, we need a lot more information than what you gave to make any definitive price calculation.
<font color=blue>It's suppose to be very clean...</font color=blue>
It sounds like you haven't seen the tractor and my estimation of a tractor I haven't seen is that it's "scrap metal" until I see it and operate it. 850 hours is only slightly more than 50 hours per year, so a tractor like that should operate like a new one and if it has been outside, it may look bad, but be perfect. You said it has wheel weights and an FEL. I'm assuming that means it does not have 4WD. If you have ever tried to operate a small tractor with a loader and no 4WD, you will see it's alot like "herding cats" on unlevel ground. See if you can get a little more info and some time in the seat. Also, you can search this forum and others for similar sized tractors to get a good idea of the prices.
JimI