I have the V8 Touareg and love it, but I got mine for CHEAP off a trade in for a Q7 TDI I sold. I get about 14-17mpg on avg driving it on the daily. I can get 18-19 highway, but that isn't easy due to heavy foot.
The things I would say is watch out for Air suspension models if you don't need it don't get it. It can be very costly down the road and that will wear and need something from a few hundred to thousands if the airs suspension light comes on.
As I'm sure you have read this will eat tires for breakfast, lunch, and dinner of you let it. 20-25K miles will be what most normal tires will wear at. If you can stay away from models with 19" wheels cause tires are very costly in that size and are limited. If everything is perfect get the 19" wheels but just find some 18" or 20" for cheaper tires if you plan on keeping it.
Another major thing with higher miles models the rear center drive shaft support bearing. If you can get under it and use a flash light from towards the rear to see how the rubber looks.
Feel free to ask any other questions. I'm in New York for Lamborghini training so I could be a little delayed. Jones knows a lot about them also of you need something before I can get back to you.