Rust in the floorpans, front frame rails is quite common. As for buying a 'runner'...I'd rather find a car with good body & bad mechanicals....esp. since you never know what might get dropped in there....Chevy LS-1/6spd would be nice. There are a few of them on the road out here. Easy 10 sec. cars...with the Z06 intake & a couple other cheap mods.
+1 on the body condition.
Look for rust in: frame, floor pans, rockers, bottoms of doors, wheel wells, under the rear bumper, around windsheild and rear window, under the hood near and under the battery (this one and the floor pans are an easy fix). I have rust bubbles in the wheel wells and one spot at the bottom of the hatch window. 5 spots total, each about the size of a quarter. I need to wait for my bonus check to tackle that one.
Look or ask about Bondo. Walk away if rust was repaired with bondo vs. welded metal.
The electrical on these cars is shitty. Expect things not to work. Consider yourself blessed if the AC works.
Most leak oil and/or other fluids. An oil pan gasket leak isn't bad. Make sure whatever oil leak the car has, it doesn't leak like a quart + every oil change.