go to a site called iselect. they have a calculator on how much extra medicare levy you will pay if you don't have private health insurance. Your friend is correct, I am fairly sure all taxpayers pay a medicare levy but then those that don't have private health insurance pay an extra levy.
when I was young and single, I did what you are doing ie. put money away in a separate account in case I needed it for health reasons. but after having a child, I got health insurance.