I agree with letting him start driving right away BUT I think that if the accident was a result of him going to fast, he needs to contribute to payments for a car and insurance.
When my car was totaled, I was in the hospital for more than a week which means obviously, I could not drive right away. It was a month before I could drive again. Having that month to think about the accident adn what could have happened made me extremely scared to drive. Its been a year and a half of therapy and there are still days that I have trouble driving on highways.
It migh tbe completely different for your son because for me, someone else caused the accident so it put the fear into me that no matter how careful I am behind the wheel, there are people out there that are not and I have no control over that adn that still scares teh crud out of me.
I would say, that if he has no fear of getting him back behind the wheel, do it sooner rather than later. BUT, I would make it very clear that he adn his friends got lucky this time and that next time might not be so lucky. I think that he needs to have some amount of fear in him so that he doesnt do something liek that again, but not enough to keep him from driving again.
The part about paying for the car....my parents paid for a new car for me only because the accident was not my fault. My brother had been in 2 accidents when he was a teenager and he had to pay for all the car repairs adn teh increase in inusrance. They made it very clear that if teh accident had been my fault, I would have been without a car until I could have paid the $6,000 OOP to cover what was not paid by the insurance company