You don't need automobile insurance before you buy a new car, but you will need it before you can drive the car home from the dealer's lot. If you know ahead of time the exact car you're going to buy, you can call your insurance agent with the information.After asking you several questions and getting all the necessary information, the agent will add the new car to your existing insurance policy.hances are, though, that the agent will not insure you over the telephone. Most agents require that you visit them in person to fill out an application and put down a deposit. The best thing to do is to establish a relationship with an insurance agent before you buy a car.