Big rig questions

[Chamberpains]

I think you missed the part where he wanted to fit his family comfortably. A Kenworth mid roof (maybe a t600 or t660) with a studio sleeper and fold up bed would supply a descent safe place for kids to buckle in and still have room. Most people don't put anywhere near the wear and tear on a rig pulling a camper compared to commercial use. So you wouldn't be replacing tires or breaks or a lot of components because they don't see the severe service of commercial hauling. The engine wouldn't see any strain at all because it would be under worked so oil changes could go out further. I would definitely stay away from the new systems because they need to be worked a little in order for the emissions to regen and clean themselves. They would be an absolute nightmare in your situation.

You asked what high mileage is on a commercial truck. well that all depends. If you take really good care of them I have seen guys put 2,3 and 4 million miles on their truck before they retire them. For the mass majority of them though, around a million miles guys have completely trashed them. You just have to know what you're looking for.