By purchasing a used car you can save a lot of money. You also could buy a loaded model with all the bells and whistles that you might not be able to afford had you bought a new car. A new car depreciates quickly in the first few years and after 3 years it is worth only about 60-70% of the original price. In fact, as soon as you leave the dealership, your new vehicle becomes a used one and is suddenly worth $1000-$2000 less.

When purchasing a new car you basically are paying for its fresh "new" aroma and warranty. However, buying a new car does not always mean the buyer will get perfection. A new car may come with problems associated with poor design or manufacturing defects that may have been already repaired during the warranty coverage period if it's a used car. The same is true for all kinds of recalls and campaigns.

Buying a used car is still a bit of a gamble - there is no guarantee that the car is accident-free, has real mileage, and was properly maintained. There may be some hidden problems like a worn out automatic transmission, or engine problems that may not have been obvious when you test-drove the car.

 from : en.wikipedia.org