Used A4/A6 buying advice?

[litewait]

Looking for an A4/A6 (maybe a Passat) for my 18 year old.

I've seen plenty of 99-02's for $2500-$4000 USD with 150k and up miles.

Really don't want to spend more as carrying collision on it will kill me with an teenage driver.

What should I look for to make sure I am not looking at a major repair before buying it, like timing belt, etc?

Are there things to avoid like Turbo and Triptronic?

Many ads say the ABS light is on or O2 sensor, those I should avoid, right?

Thanks for the help.

[turpal]

I`d assume you looking to buy a petrol one as fuel is cheap where you are.Make sure all the lights come on when ignition on and go off once the engine started especially yellow engine sign.Allways start the car from cold so you can hear any funny noises.Turbos ok if pull well and no oil leaks etc,I`d avoid tiptronic thogh but thats me.