Unfortunately, your son is going to have a very difficult time trying to purchase insurance. Many insurance companies will not accept a foreign or international driver's license. The insurance companies that accept a foreign or international driver's license to purchase an insurance policy will require him to purchase a valid U.S. driver's license within thirty days of the policy's inception date. Otherwise, they will cancel the policy. Also, I do not know of any insurance companies who will write an insurance policy for anything less than 6 months.