Rust! Should I sell it?

I have seen and repaired much worse. My question to you (I always ask this) is, "How much of the work can you do yourself"? If you can weld and repair the rust yourself, the repair will be easy and not terribly expensive. If you have to hire out rust repair, it is NOT cheap.
How much rust is repairable is different for different people.
I know a guy that had a turbo Firechicken that had some rust. He sold the original interior, intending to strip the engine and disc brake rear axle. Then he stopped at a restorer somewhere by Seattle and saw what he was restoring, which was in considerably poorer condition. I had to ask if he was going to repair the rust now and get another interior. Got a couple of expletives in return. He did strip it and scrap the body.
Same guy had a tree fall on a 1940 Olds Coupe. Looking at Olds production that year the coupes had a fair number built out of Olds production. When looked at against the General's total production, it was a fairly rare auto. It would have taken a fair bit of work to straighten the roof out, but with some metalworking skills it could have been saved. He cut the body up and took it for scrap. I have the frame. I got pissed with him over a few more things and refuse to talk to him.