How severe can rust issues be on a Newell Coach?

[Chipper]

After looking a couple of Newells and a couple of them appear to have rust and corrosion issues. After driving a late eighties with the cracked frame, I am now inspecting every single Newell for the possibility of frame cracks, rust and corrosion. Have many of you owners done these kind of inspections on your Newells prior to purchase or did you possibly overlook this area? Both sellers acted as if there were no concerns and at the same time didn't know of anything being an issue.

I have heard of certain buses having rust issues like the Eagle in rear areas and now I'm seeing something similar with certain Newells. Why is this, and what could be the cause of concern?