Is this a good Class C?

Maybe or not. We bought a 2003 Itasca(made by Winnebago)30 ft. Class C in 2013 with 20000 miles for $23000. So it was 10 years old and yours would be 8 with twice the miles. The 2 years isn't much of a factor. And ours has 2 slides. I think that Ford 450 chassis with the V-10 is good so I wouldn't worry much about that part of the motor home. But, I trust the Winnebago "quality" way more than the Chateau but not sure if you should pay much attention to that. All I really know about Chateau is that campground talk is that they are sort of a low end motor home. Hard to be specific about that but examine cabinets, doors, windows etc. So do you mean actually selling for $30000 or just that's the asking price? Sounds high to me. If asking 30 you might offer 22??