One thing I forgot to include in my above post was.....I WOULD drive the car until it is no longer drivable. These wagons last and will serve their owners well. About the only major thing that will take them down is rust.
Here's an ignorant question when it comes to looking at a car and checking for rust. Do you go to someones house and bang on their car/frame with your hammer & chisel? These are the kind of methods i saw when googling it. Ideally the seller would be 100% honest, but then again, they may not know or don't want to tell. To protect yourself though, what is acceptable? I'm sure there are dead giveaways in terms of severity but what's a way that's in the best interest of both parties?
I'd take a mechanics micrometer and measure the height of the rust scales? A little more discreet, but you'd know how much sheet metal was left.
I picked up some rust stripper and rust converter today. I also have por 15 which I plan to save for warmer weather. Do you recommend I use the converter over the rust or the stripper to try and rid some of the affected areas of rust? I need to re-register the wagon sooner than expected.