That depends on the make and model of the car, along with other factors such as mileage. If you can swing it, however, try to find a car that's at least two years old. Cars depreciate by a third of what they cost new after just 18 months. Buying cars that are around five years old can be an affordable option, because they are typically still in good condition, have already taken a big hit in their depreciation, and should have well under 100,000 miles on them.