Where is the rust popping up? Are the bubbles soft ( like under the thickness of paint) or hard ( like under thicker putty )? Or are the bubbles visibly brown like there was a paint chip left unattended to?

Bubbles under the surface is a sign that the rust is occurring on the other side of the metal and is far worse than you can see.

Roll the windows down, use a flashlight with a tight beam and shine it into the window slot, usually you can see to the base of the door. Look for putty pushing through any rust holes / dents. Lift the carpets / push around the floor, look in the trunk wells for rust.

Usually those of us in the rust belt go to your area to find a non rusty car. But, given galvanized steel wasn't used much in the early years damp and rain water will rust older cars.

What is it worth? I don't know as they are not my thing. Rust work is expensive , hanging mechanical parts on an otherwise solid shell is no big deal.