i want to buy this car.it has 71000 mileage. do you think the turbocharger still alright?

Probably OK, I would not worry about it.

Should be, but the only way to know for sure is to drive it. The clutch should feel a bit different that your typical one. The term "squishy break pedal" has been thrown around to describe it. Also make sure that it effortlessly shifts through the gears. Pay special attention to reverse. Other things to look at would be a timing belt and waterpump replacement. At 71k the car should be due for it. They make several "kits" to replace the two and those cost about $300. Having it done from a dealership is pretty price (sometimes to the tune of $2k) They're easy to replace together, and it's definately something that you can do yourself. Give the car a drive and hit me back if you've got any more questions.

its all good, at 75k miles you are going to want to get the usual check up, that is where your timing belt and a few other things might need a change. mine has 125,000 miles and it still runs great. turbos are going to start to die at 150,000. but trust me, your gonna want a new turbo and feel the power that a A4 can produce

Depends on the quality of the maintenance that the previous four owners have done to the car. As long as they have been religious about changing the oil on time. The k03 (the turbo) in that car should be fine if the regular maintenance has been performed. Also find out about the timing belt; if it has not been done yet DO IT ASAP. Check the transmission. Plan on doing all the fluid changes (Coolant, Transmission, Rear Differential). The only other problem with the 1.8t is that some of them have "sludge" problems because of improper oil and maintenance. You can tell by taking the valve cover off and looking at the cams and valvetrain parts in the head. I love my Audi but the maintenance can be a bit overwhelming. They are good reliable cars but the do require proper feeding and care to perform correctly. I'd be a touch wary that the car has had a new owner roughly every 17k miles or so...

This car has only 71000 km. The time recommended for changing the timing belt is 160,000 km so why are you suggesting it be done ASAP. Makes no sense to me.