AH rust, it's everywhere. It's just part of the natural order or whatever you might want to call it. Steel will rust/break down even in a vacuum chamber at zero humidity. So everything that is done to seal/treat/coat or paint is only slowing down the process. With that in mind if you see rust and plan on keep your vehicle don't watch it do something to slow it down.
Now this is where the arguments get flying. I've been trying to find an affordable maintenance method for the last 40+ years. And yes if the manufacture treats and coats the steel right in the first time, then you have a head start.
IE: My 89 Probe sealed/coated and painted on the bottom side and Ziebarted, still after 8-10 years found a small hole in the floor pan. The weak point the spot weld. I've been told the that the high heat of the weld causes a molecular difference that causes, well sort like galvanic action.
If you are fortunate to get around cars buffs that restore/maintain collector type vehicles, They have all sorts of tricks to slow down the process.
But first and foremost don't just watch it, do something!
I've also learned that paint is porous/breaths! If you can find something called "Miracle paint" & another similar product "Por_15", it I believe is a coating that I've been told seals and cures.(like epoxy) This is only for the underneath and out of site areas.
IE I use to work with guy that has it on his vintage car. The battery tray had rust (of course) he wire brushed the loose rust off, bushed on the miracle paint. He knows I'm a skeptic about this easy method, well after 8 years it still looks like new. It's a 60's something Olds drivable show car. BUT don't get the stuff on your hands, it only wears off!
Then there is the interim step during before/during/after (a around to it) winter when I spay, PB Blaster! Like I said, don't watch do something. Or get get some of Rust stopping converting product that the autostores carry.
"I hate Rust" Paul
I though there would be some rust somewhere, 
but could not find any. 