OK, I'm going to be the dissenting voice here. There are other early 140's around, and some of them will have a lot less rust. As others have said, what can happen is that you calculate $$$$ and time based on what you can see, and when the body guy or you get into it you find much more damage.

I speak from the two experiences of a Duett that just got out from 2 years at the body shop, and a lovely garage kept '67 140 with no body rust at all, that was $500. It had developed rust pinholes in the gas tank, so it couldn't be shown to run. My purchase was based on faith in the fixablility of the B18, and I was driving it a week later...

Scary rust pictures, including rat nest in the spare tire well (!) available:

140 on a trip: http://picasaweb.google.com/53Bentlley/Sept09TripToColmbiaGorge?authkey=Gv1sRgCLuftaKZit2EYA#

Duett rust:http://picasaweb.google.com/53Bentlley/Restoration1#