Should I buy an Infiniti 2006 M35 WITH 85,000 miles for $21,000?

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