Moving out a few weeks before I'm 18?

Well my parents are very controlling, there are many rules imposed on me and I would just like to move out after high school,right before University. They obviously won't abide this as I can't move out before I marry someone of their choice. Argh I'm not even allowed to date, I can't tell them anything and I really just want to start living for myself, and control my own life. Should I move out? How should I do it (I'll most probably leave and never talk to them again)? How much do I need to have saved up? What kind of things should I have in mind before leaving? And what if I move out before I'm 18, like only a few weeks, a month at most... is that legal? Can they ask the cops to bring me back? By the way this is in Sydney, so does anyone know the laws regarding this particular issue? Please help!!