Getting comparison insurance quotes is far different today than it used to be. Historically, it cost someone money to get a look at rates from a company. In their view, they were working to get you these auto insurance quote comparisons so they should be paid for this time, whether you go with a different company or not. Typically, a company would waive the quoting fee if you bought their plan.
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.
Minimal insurance policies cover only third parties (including the insured person and third parties carried with the vehicle, but not the driver, if the two do not coincide). Also the third parties, fire and theft are common insurance policies, while the all inclusive policies (kasko policy) which include also damages of the vehicle causing the accident or the injuries. It is also common to include a renounce clause of the insurance company to compensate the damages against the insured person in some cases (usually in case of DUI or other infringement of the law by the driver).
Liability auto insurance protects you from that worst case scenario by providing a cushion between your assets and the amount you’re on the hook for. For this reason, choosing the right auto liability limits is the most important part of your car insurance quote comparison. NerdWallet typically recommends having at least as much liability coverage as your net worth.