When checking for rust, make sure you pull up the padding in the cockpit. It's a prime area for rust. I purchased a van that I knew had some surface rust underneath and a little on the quarter panels, which didn't concern me. What I didn't know was the cockpit floor pan on the passenger side was 50% rotted out with some rot on the driver's side.
The padding that Ford used under the rubber floor gets soaked and traps moisture.
2005 E350 Super Duty Ext Wheelchair Van
2002 Itasca 35U Motorhome