Thinking of buying a 2006 Audi A6 but it has repair codes P2006, P0335 and P2101. Are these expensive fixes? Worth it?

Stay away and save your money.  14 year old Audis are junkyard ready.

You'll end up spending more for the repairs then they are asking for the car. 

Tell them if they fix the car you may buy it. If they decline, walk away.

2006 indicates a stuck intake runner flap.  0335 says the crankshaft sensor isn't working.  2101 concerns the throttle actuator.  

If these codes are active, the engine may not run or it's in safe (limp along) mode.

Run,  Forrest, run.  

Audi's are good for about 3 years, then they start having problems.  I really love the way they look, and can afford a new one, but I'm used to very reliable cars and can't justify it. 

No it's not worth it, and stay away from dealers that sell cars like that.