So in continuation of my quest, my brother is going and looking at a Fiero out in MI. What in specific should he be looking for besides rust in the trunk area?

Check the belly pan where the rear frame rails connect to the belly pan. The frame rail often rust out below the battery.
Look at the front cross memeber right above and between the top control arm of the front wheels. There is a bracket there that can rust out really bad. (pre 88)

Battery tray and check the metal rocker panels above and outside of the coolant tubes.

Those are some of the places you can find bad spots..

Make sure the car hasn't been jacked up by the coolant tubes.

I'm afraid you're going to get something rusty buying a car from here (Michigan)

Ok, but other things too not just body. Heres the listing BTW http://toledo.craigslist.org/cto/1533182946.html

Check the dust cap under the dash for a leaking clutch master as well as the dust cap of the clutch slave for fluid.
Headlights go up and down ok.
E brake works. (cables not locked)

I know you don't want to hear more frame & body suggestions, but pretty much everything can be replaced with relative ease except the frame. You'd do yourself a real favor if you brought along a 7mm socket wrench and removed at least one of the rear wheel well liners and had a look (about eight screws). One look there and you'll know whether the car's worth buying or not. To get the liner out, you'll also need a pair of needle nosed pliers to release a herring-bone style wire-loom anchor that just barely pokes out into the wheel well around the two o'clock position when facing the LH wheel, and another one at about the 10 o'clock position when facing the RH wheel. This is the kind of stuff that is hidden very well by the liners: