Yeah I hear you, I still have three cars between my wife and I but we use all three. Well kinda, her POS Kia sits most of the time ha I can't wait for the lease to be up.
Anyway being in Cali rust shouldn't be an issue but key spots to check are: strut towers, rocker panels right behind the front tires, and the floor near the subframe.
First off no automatics. The DSG is great, but Volkswagen couldn't build a slush box automatic to save their life. Since that's all they had till the Mk5 gti count all autos out.
Next is maintenance. If the seller doesn't have printed records proving the timing belt & waterpump has been changed in the last 80,000 miles or five years it needs changed asap. This is true for them all other than VR6, which have chains instead. This is a very important bargaining chip for both price and gives you an idea if the PO had a clue about taking care of the car. Other red flags are green coolant (proper VW G11 or G12 is pink), oil leaks, mods, shitty clutch or shifter slop on pre 2000 cars (2000 and up the slop is an easy fix).
Just drive the car ten mins or so and make sure it seems tight and doesn't have mechanical noises or anything that would make you question its reliability. If it's low on oil or the oil is black walk away. Pretty basic stuff but be defensive and check things out the best you can. I've bought and sold lots of cars, the best ones come from an owner who's had it a long time and knows the maintenance history. It's a bad sign if they "only owned it a few weeks".
Anyway post some cars you find here I'll check out what I can from the ad. It doesn't have to be new to be a good car