you have to phone an insurance company and find out! it might be slightly different if you were driving a fiesta to a rolls ryce. Thats how insurance companies work - you tell them your details and they come up with what is called a "quote" - ie they tell you how much money they want
Old bangers are often more expensive to insure than modern cars....an old car is much easier to steal... so I believe you will find a new car cheaper to insure ...it wont be that cheap though...try
It also depends significantly on where you live and where the car is kept at night (on street / driveway).
It's a ridiculous question because the range of possible answers is phenomenal. It'll almost certainly be at least four figures though (I suppose if you live in the Shetlands or something and the new car is a Smart Car it might just about not be).
Work out what kind of car is within your budget, then go for something cheaper because your first car at 17 will have high insurance! Have a look through the range of insurance comaprison sites.