If your son lives with you, you need to notify your insurance company that he is an insured driver living in your home. However, in the case of his own vehicle, he is held liable for his actions behind the wheel. He needs his own insurance policy if the car is in his name. This will make sure that he and his vehicle are protected.
Remember, it is important to remember that if your son borrows your car periodically, he needs at least liability. Again, contact your insurance agency to get a specific answer for your unique situation.
At first glance, it would seem that if your son can have a title in his name, he should also have his own insurance policy. In most cases, the person that purchases the car needs to show proof that they also have an auto insurance policy in their name.
Issues could also arise during the registration process, as well.