I'd be surprised if the car doesn't have antifreeze in it already - it's typically something that is put into all brand new cars, and not something that the owner has to put in themselves (only top up perhaps). Check by opening the bonnet, and looking to see if the water is a blue/green colour. If it is, then it has antifreeze in it. Don't get mixed up with the radiator water and the windscreen washer bottle though - the windscreen water could be blue due to the screenwash!