How old do you have to be to drive a classic car?

In most states in the US, you need to be 16. There are a few where you would have to be 18.

If you or a friend of yours does not own the car and you're wanting to rent it, most rental agencies have a lower age limit below which they will not allow you to rent a car at all. In the past, this was often 25 for the major rental agencies; it's now lower (20 or 21 in many cases), but those under 25 may still find themselves being charged higher fees and/or only allowed to rent certain types of cars. "Classic" and "Exotic" cars are highly likely to be among those that are not available to younger drivers.