Should I purchase a 2006 Infiniti M35X for $21,000 @ 85,000 MILES?

I am looking to purchase a used vehicle and found this offer. A used 2006 Infiniti M35x AWD with 85,000 miles for $21,000. Is this a good deal? How long do infiniti's usually go for? the car is in great condition. Please advise. Thank you in advance