Your only 18 for heavens sake! Take a year out and explore the world! Then go to college or university and enjoy yourself. Graduate in a few years time with a degree in something that you like doing and will be applicable to your future. I suggest something IT based with a business studies minor for maximum end-employability. You will then be able to walk into a job in IT or possibly start a company of your own with some of your University friends.
If I had my time again, it's what I'd do!