<p>Well, those are very broad questions! </p>
<p>As for what each service does, going to each service’s website would be a good start. [Join</a> the Military - Military.com](<a href=“Join the Military | Military.com”>Join the Military | Military.com) also can give you a general overview.
My advice to him would be to figure out what kinds of things he wants to do, before looking at specific services. Some career fields are specific, while others are common to multiple services. For example, every service has helicopter pilots (but the numbers and missions vary). Only the Navy has attack submarines. Only the Air Force has land based ICBMs. etc.<br>
Aside from what his interests are, he may also want to consider whether he wants to be an officer or go enlisted. You could think of officers as the “corporate leadership” in some ways. As time goes on, officers are less likely to do much “hands on” stuff, and more likely to be leading and managing larger teams. The same is somewhat true of enlisted people, but the chances of them doing field work for a large portion or their career is much higher. Some services also have Warrant Officers, which is in between officer and enlisted. Some services use warrants as technical experts in their field (Army aviators, for example). The pay and benefits are also quite different for each choice.</p>
<p>The federal Service Academies are for their specific branch (with the exception of the US Merchant Marine Academy). Transfers between SAs are only semester long. You cannot simply switch partway through, and pick up partway through another. If you quit within the first 2 years, you do not owe a commitment. If you leave after that, the government can have you pay back your educational costs or have you serve in an enlisted position (at their discretion). There are limited opportunities to commission into a different service upon graduation (usually in the single digits out of ~1,000 graduates).</p>
<p>All of the SAs are focused on providing a good education and leadership training. They all rank fairly highly in several categories. Realize that they all focus quite a bit on technical classes. USAFA used to be called “the little engineering school in the Rockies” for example.</p>
<p>For people going enlisted, they go through MEPS, which includes all the medical screening. Service Academy cadets have to pass the DoDMERB standards (or get waivers) prior to gaining an appointment. DoDMERB has its own site for questions and specifics. Generally, things like braces will not be a problem. Chronic medical issues can be (asthma, diabetes, etc).</p>