At 18 years old your son should now be considered an adult and no longer a minor. Since he has moved out of your household and resides elsewhere in most cases he would be responsible if he gets into an accident.

This is unless the car he is driving without insurance is a car that you own. If your name is on this vehicle then if he was in an accident and could not pay for the damages he inflicted on another person or property you could be held responsible. You would be vicariously liable since as owner you are responsible for those who drive your vehicle.

Speak to your son about the penalties for driving without insurance, which can include, depending on what state you are in, the vehicle being impounded, license plates revoked, license suspended, and fines to name a few. He can search for affordable car insurance by following this link.