If a friend wants to use your car is it possible for him to buy his own insurance to drive your car?

Yes it is very possible for your friend to get insurance to drive your car. There are 2 ways, the first is called a non-owners policy which will only provide liability coverage, and no property damage to your vehicle. The second is to get a policy on your vehicle which is now available in most states, without having insurable interest. The non owners policy is the least expensive.