What are some common places for rust on a thirdgen. I was looking at a 90 iroc yesterday and it didnt look too bad but you could start to see some paint bubbling on the 1/4 panel and near the wheel wells. What other places should i look at? Anything else i should do to make sure that car is in good shape? Thanks!

Look around the antenna, pillars leading up to the roof, look at the sides of the roof itself. If IROC or Z28 take the insulation off from under the hood and look at the area around the scoops, also look at the front edge of the hood.

battery tray

Rear Wheel Well edges. They go first.

Hatch channel soon follows. Also look at the bottom edge of the doors.

My t/a has even developed rust in the doorjambs and of course the floorboards

Mine has a very small spot right along the back edge of the t tops on the passenger side. If it's a t top car take the tops out and check around them.

i have seen a bunch at the strut towers, and front wheel wells of mine and many other cars.

i also have some rust right in front of the passenger door, behind the front 1/4 pannel.

the roof..
the roof..
the roof is on fire

well maybe not, but it's rusting all to hell.

Also I haven't had any major issues with this, but under the rear wing is a common trouble spot.

On the metal spots.

Any spot is vunerable, but the most common are pretty much highlighted above. The lower radiator support is also a major spot. Even my IROC had a lot of rust on the underside of the lower radiator support. Crap collects in there and stays moist.

Floorboards, rocker panels, wheel well openings, door bottoms, etc. Behind the ground effects is also a major issue, and is often unnoticed.

If there's just a little rust bubbling, that's nothing to worry about unless its the previous body work that's bubbling... that could indicate that it was repaired improperly last time, which means 20 other spots on the car probably were too. If it's just the rust bubbling the paint directly, I'd consider it an easy fix if done right (sand blasting).

The body is not as important as the undercarrage. Rust repair on the undercarrage is insanely expensive unless it's just surface rust that can be sand blasted. On a unibody car, the chassis strength is very important, and if the floors & rocker panels are going south, the rigidity of your car can be comprimised.

Definitely pull off the t-tops and check (if it is a t-top car). Also, inside the front lip of the hood, just above the headlights seems to be a common place for rust too.

floorpans, and any where else standing water can be for days, maybe even weeks..