Joining military/college?

I don't think it's a good way to go about it. Either:

1. Look into an ROTC scholarship. These are very competitive but are easiest to get if you are enrolled in a science, engineering, or technology major (or nursing, for the Navy) (but not, typically, biology; only sciences that are actually useful to the military). You need to be at least 17 (with parental consent). If you are awarded a scholarship, the military pays for your college, room and board; you take about a minor's worth of classes in military science in addition to your major requirements. You have training a few mornings a week, and during the summers. After you complete the program and graduate, you have a four- to seven-year service obligation (depending on the branch of the military that's your scholarship is with).

Most colleges have either a ROTC program on site, or an agreement with a nearby campus that hosts ROTC classes for several area schools.

Of course, it's very late to be thinking about applying to four-year colleges now; most application deadlines for the fall term are January 1, but it depends on the state. The ROTC scholarship application deadline is February 4.

2. Join the military when you graduate high school, but don't expect to be able to take very many classes while you're in service. It's a full-time job, remember, and a fairly strenuous one. Also, if you're pre-med, you won't be able to take any laboratory science classes on-line; your grades are of the highest importance, so your focus should not be divided between work and school; and you'll need a lot of hospital volunteer work, physician shadowing, and medical research work, which you (probably) won't be able to do in the military. Don't listen to the recruitment officers' promises; they're completely meaningless. Once you've signed up, the military will put you where it needs you, not where you've told them you want to be.

Once you've served, you can get your college paid for according to the GI Bill.

The military will not "reimburse" you for classes you've taken before you joined, although you can certainly use your paycheck to pay off your student loans.

3. I'm assuming you're just going to community college for a year until you're old enough to join the military? If you are old enough when you graduate, just join.

If not, don't graduate early, if you don't need to; you might be able to take some dual-enrollment classes for college credit during your senior year.

Or, do any relatives live near a "better" community college, so you could live with them and go there? It might cost a little more, but there's little reason to pay to go to a community college that doesn't even have the classes you need.

Or you could just work, live at home, and save your money until you're old enough to join.

ROTC will pay for your college. it's a scholarship. then you serve as an officer for five-ten years after graduating and completing training.

All pre med classes must be taken at a university. Medical schools won’t accept them if you don’t.
You take only general education classes for transfer at a CC.

The military pays you a salary. What you do with that money is up to you. They will not be giving you extra money to pay off student debt,

I would get a meeting with admissions office at your community college and talk this over. You can also get a meeting with admissions or a college adviser at the college you have been accepted at. They can help you with all questions you have
Most military will accept you after taking 12 college credit hours. Which can be done in one semester at a community college.
You are not going to be able to take any prerequisites for medical school at an online school. I am going to say medical school is not going to accept an online Bachelor degree,