Have you looked into ROTC? They will pay for you to get your Bachelor's then Commission you as an Officer.
Figure out what you would like to do then report back and the group can give you more specific advice. I enlisted as an E-1 at 17 in the Army and left as a Captain 03E so I can give you advice on that branch. One thing to remember is the recruiter is looking to just get you in and will push certain fields. The Army is always short on MP's so it is an option.
Allen