If the younger driver is covering his own costs, it might be cheaper for him to take out his own policy but include one of the older, lower risk drivers from the household as a named driver (as long as the older drive will use the car). However, if the older driver is footing the bill for both policies, multi-car insurance may still work out cheaper.
In case there are any changes that need to be made in the policy such as address change or any particular changes regarding the automobile or its usage, it could be done by an endorsement by the insurance provider. You need to submit a letter to your insurance provider along with the proof of the changes so that you could obtain the endorsement. There are few endorsements that might charge an extra premium from you.
When the premium is not mandated by the government, it is usually derived from the calculations of an actuary, based on statistical data. The premium can vary depending on many factors that are believed to affect the expected cost of future claims. Those factors can include the car characteristics, the coverage selected (deductible, limit, covered perils), the profile of the driver (age, gender, driving history) and the usage of the car (commute to work or not, predicted annual distance driven).
Vehicle insurance (also known as car insurance, motor insurance, or auto insurance) is insurance for cars, trucks, motorcycles, and other road vehicles. Its primary use is to provide financial protection against physical damage or bodily injury resulting from traffic collisions and against liability that could also arise from incidents in a vehicle. Vehicle insurance may additionally offer financial protection against theft of the vehicle, and against damage to the vehicle sustained from events other than traffic collisions, such as keying, weather or natural disasters, and damage sustained by colliding with stationary objects. The specific terms of vehicle insurance vary with legal regulations in each region.