Not overly familiar with 2010 model, but if it's 2.0 TDI, then 168bhp. Later models from 2012 moved to 177bhp. 3 litre V6 TDI models are relatively sought after with 242bhp, so plenty torque. Not sure when Audi Drive Select was introduced. It's on my 2012 car and nice function.
Let's assume it's a 2.0 litre model. Paperwork is everything. At 8 years old, then you're potentially looking at cars in 80-100k miles territory. Sure it's possible to find a car on less miles, but that's average. Timing belt needs to be done every 5 years or 60k miles, along with auxilliary belts, tensioner pulley and waterpump.
The rear diff gear oil if at 100k mile level could use an oil change. Again, that's my preference. If inspecting underneath, then diff should be dry. If it's wet, then there's the chance of leaking drive shaft seals.
Check bodywork closely. Any rust will be evident at this age, so front arches, tailgate and door bases are known spots. The bodywork is galvanised, but it gets expensive to repair.
The Quattro system itself is maintenance free to a point. As mentioned, the rear diff and transmission would benefit from a gear oil change at 100k miles if you plan to keep long term. Check tyres for even tread wear. If you haven't driven a quattro before, then the car can crab at full lock. Change tyres on all 4 corners to avoid over-winding the diff.
Transmission, I can only comment on 6 speed manual. Should be easy to change gear, still tight with no slippage.
Suspension wise, at 100k miles, then probably original shocks all round. The car uses upper and lower control arms, ARB links. All this wears with use, so a sloppy drive, slack in the steering (tie-rods) or tell-tale clunks can be difficult to identify unless you're mechanically minded. Meyle HD (4-year warranty) or Lemforder can bring it back to factory standard. Will need a 4-wheel alignment afterwards. Bear in mind these cars are not overly robust, so cars with tow bars could have been hauling horse boxes every weekend, so rear springs can break.
Service wise, you want receipts and lots of them. Oil changes, then I recommend 10k intervals using fully synthetic oil and filter change. Fuel filter every 20k miles. Air filter every 10-20k miles. Pollen filter every year. Glow plugs, then leave well alone. If you know someone with VCDS, then definitely worth scanning.
This is totally a buyers market as diesels are getting a mauling just now, so if you can get a younger model, that's what I would look at. Specification should include xenon headlights and heated seats as a must. Bose speakers would be nice, as is satellite navigation, leather or alcantara interior, electric folding mirrors or power boot. One word if warning for cars with panoramic sunroofs, they can leak, so you've been warned.
Anyway, best of luck.
