If you want a wagon, get one with the best body possible. Avoid a big project. I now wish I had shopped around longer and invested more up front for a better wagon than the one I have. My wagon isn't actually all that bad, but the problem is that replacement parts are usually non existent.
Some rust in the window channel around the rear side glass? Be careful before you remove that side glass, you may not be able to find a rubber seal to reinstall it. Rust in the lower right rear quarter? They all have that and its where the spare tire is located on many Mopar wagons. There won't be a patch panel available as its usually not the same quarter as a sedan or coupe. Rusty tailgate? Yeah, that would be easy to replace if you can find a better tailgate. But expect to spend more for shipping than you do for the tailgate itself if you can find one.
Wagons are very cool and there are very few left. If you want one that you intend to keep, pay extra for a good complete car that is as solid as possible. Be extremely careful of any project cars you look at.