What about this 71 Dart?? Advice?

Since he says it needs a rebuild and doesn't currently run, you might as well figure you would be buying a painted shell.
He also says it needs the rubber, so figure the windows may not even work right, and could need all new body to front and rear window rubbers along with wiper pivot seals and all.

That would be a need to see it in person car for sure.
If the body and paint were in good shape it could be worth it since paint is ridiculous these days.
You would just have to make sure all that shiny paint wasn't covering up a rotten body.