"Good" is in the eyes of the beholder

When I first checked out the car, things looked good. All the body panels were in pretty good condition, the engine turned and the interior of the car looked to be in good condition. Upon closer inspection of the car, however, one slight issue revealed a big problem, something I was not planning on at all.

We decided to clean out the insides of the car (there were some leaves and debris from the car being stored outside under a tarp) and noticed an inch of water sitting under the chair. Wanting to dry this out, we removed both seats and found the seat tracks completely rusted. Trying to check the extent of the damage, we removed the interior carpeting (which had been thrown on with lots of hot glue) to find bad rust throughout the floor panels and along the edges. We could see the bottom of the garage through the floor panel, not a good thing. From underneath the car, only a rust hole was visible, but now with the interior removed, it's bad. Oh, and the sitting water had made the car stink...

Even better, it looked like the original car owner had tried to quick fix this "little" rust problem by covering the floor panels with flash metal and just folded it in to place. It was bolted into place by balling up some of the same metal material and shoving it through a hole. Awesome fix. Looking at the driver side, given a few more years of usage on the car, I'm pretty sure the driver seat would have just fallen through.

Car summary:
Engine: It turns and has been known to start within the last year.
Exterior: All panels are present. The original color was red, but the car had been repainted to silver. Now that I know about the rust on the floor panels, I'm worried that the silver paint may cover up some existing rust. I wouldn't be surprised it it did.
Interior: Like a Monet. Looked good from far away, but up close will need to replace everything.