On a car with no visible rust, have you seen serious frame rot? I live in NY and everything spontaneously combusts when it becomes 15 years old from frame issues, so im kinda paranoid bout this '92 Im looking at. The car has no rust and no holes anywhere on the body.

I know just what you mean. I live in PA near the NY border. Salt galore in the winter. I bought an 84 Camaro in 95 with hopes of some major modding and paint. The frame didnt look bad when purchased. Two springs later I had a massive hole in the frame just before the driver'* rear tire and it failed inspection. I couldnt get a shop with DOT certifacation to touch it. One even pointed out some other minor area'* coming through. The undercoating hid it on the outside till it was to late. Makes me want to whack anything used with a ballpeen hammer if I were ever to buy used again.

Maybe I should just get an exceptionally rust-proofed old E-class. Yeah it'll cost more to keep it on the road but I can keep it for 10 years easy....