How long do Nissan Sentra's usually go?

Never, Ever buy a car with more than 100,000 to 120,000 miles unless you practically get it for free. Id rather buy a car from the late 80s with 70,000 miles than a 2000-anything with 150k on it. The true age of a car is more correlated to its mileage than its calendar years, especially in areas away from the east and gulf coasts.

A 3 to 4 thousand dollar Sentra would be around a 2002 to 2005 year model. Lots of wear and tear have the engine checked out by a third party technician. If you buy the car ask the former owner to pay for the check out. If the technician finds a bad issue you saved plenty. A 7 or eight year old Sentra for 16 year old is a perfect starter car as are many Toyota's, Honds's and Mazda's. If the child gets into college they may need another better car then. There are some really cool cell phone tracking devices that can be computer at home tracked with special soft-ware.

Make sure to check the blinker fluid, it should be brown. Also they had problems with the thermocouplers, so make sure they were fixed under warranty too.