Newbie needing advice about buying used

Hi All,
We've never owned an ATV before, and we want to get one used because we just don't want to spend so much on new. I'm shocked at how slow these things depreciate! We are looking for a 4X4 utility quad to run our dogs on a very hilly 115 acre property that gets very muddy in the winter. We'd also like to haul, mow, disc, whatever these things can do in a ranch setting. So, we need enough power (what the minimum cc's would be I don't even know). I am finding that even 6 to 8 year old quads are still at or over $2500!

One guy offered me a '96 Yamaha Grizzly 400 4x4 with 2200 mi. on it, for $2000. What is the life expectancy of these things? Is that considered really high mileage? I know how it was cared for makes a difference, too.

I guess I'm looking for advice as to minimum engine size to do some heavy work, and what kind of hours/mileage is considered way over the hill! Also, recommendations as to which makes/models have better longevity, dare you offer your opinion (I know it can get heated with that regard, so be nice!)

TIA