The Military isn't a decision to be made lightly, nor is it a decision to be made without your partner. Those are big red flags for me, and if he DECIDED without you, rather than came up with the idea without you, then there needs to be a major come to jesus discussion. That sort of thing shouldn't fly. Ever. Especially if you are thinking of joining the military of all things. I would be concerned he would ask for certain deployments, want to take orders and accept them without you to a place you can't go, make certain decisions about his job that wasn't run by you first. No, that does not fly well for spouses/partners in the military.
Now, as for your questions...
How often is he actually going to be here?
For the first several weeks, he will be at Basic Training. If he is going to fail, it will be here. They crack down on everything. What you eat, when you go to bed, who you talk to, how you dress, how fast you run, etc, etc. You will be allowed to write plenty of letters, but he will not have access to a computer. He *might* get a phone call once a week (ours were on Saturdays) if he has a good behavior rep. You will get to visit him for Graduation, then he ships of to what the AF calls Tech School.
This is where he learns his job. Depending on the career field, he might be gone 3 months, he might be gone 2 years. If he doesn't have a college degree, doesn't score high on the ASFAB, he probably will only be gone 3-7 months. Those are for the lower career fields. He will have plenty access to a computer, you can skype, he can have his personal phone, you can visit if he's on good behavior on the weekends. Just like being in a college dorm. After all that...he gets stationed at his first base. How long he will be gone after that will depend highly on his job.
For most lower level career fields...it's honestly pushing paperwork or something similar. 9-5 job.
How often will he be at sea?
Believe it or not, but the Navy doesn't actually go out to sea very often. Same with the Air Force. We don't hit the skies all that often, either. But, again, it depends on his job.
Will he be stationed at a port in another country?
Possibly. He will have a Dream Sheet, and sometimes they will give you the location you want to go to. We had Italy on ours, along with a lot of western States. Well, we got Montana first, then Italy. Keep in mind, many Navy bases aren't ports at all. There's one in Memphis, TN, for example. No where near an ocean.
Will it be one I can stay at?
Most bases/ports you will be able to stay. The ones I know of that you can't are those in War Zones and Korea. But most countries you will be able to, like Germany, Italy, England, Japan. Pretty much all states you can go to.
Will he be moving around a lot?
Maybe. Some people end up getting moved every 6 months to a year. Some end up at the same base for 6 years or more. Depends on his job, and the base he gets stationed at.
Should we go with him if we can?
If you get married before he leaves, the military will ship you with him free of charge (either pay for it or reimburse you). If you are not married, you are responsible for your own travel. It's up to you if you want to go with him. Personally, I enjoy moving around and seeing the country/world.
Should we live on base or stay here?
Off base, it's the same as any other house, apartment, or living somewhere new. You can have your kid go to school on base or off base. Personal preference. But he will get a BAH to cover off-base expenses should that be the decision. On base - most everything is paid for. Utilities, trash, rent, everything. No bills. But he gives up his BAH. BAH is based off of the Cost of Living in each area. In our area, it is $808 per month. In California, however, it may be $1500 extra a month.
Do most Navy wives that are mothers work? If there kid isn't in school yet how?
If you want to work, you are more than free to. Some work, some don't. Depends on your way of life. As far as kids, there are plenty of resources available for your disposal at each base. Most bases are like little towns...grocery store, couple fast food places, schools, libraries, child care, etc.
What do I need to know, what should he know?
In order for things to go as smoothly as possible, you need to be married. The military will take care of ALL of you...if you are married, or if that is his kid. Otherwise, you will be left behind to pay for travel and everything else yourself. By marrying him, the military takes care of not only him and the kid, but you as well. And there's a ton of benefits, including "free" healthcare, they pay for your travel, the bases are huge sources of information about everything.
Now, when you get on base/port, you will probably find yourself NOT wanting to socialize on base. In my experience, most military wives are the typical spoiled brat women, sitting around reading Cosmo and discussing how they will spend the money if their spouse dies. No joke. There will be men out for your attention, women out for his. Cheating is pretty common place. Like going to highschool all over again. However, every base is different. Smaller bases will be worse, larger bases won't be so bad at all.
The Navy and the Air Force don't get deployed nearly as often as the Army or Marines. The Marines have no home bases, so they get shuffled around a lot. The Army is our infantry, so they are typically the first to deploy if a war is going on. The Navy and the Air Force are either pawned off to the Army/Marines for support, or they sit back and do the tactical side of things. For example, the Air Force is called the "Chair Force" because people think we don't do mch. But, we're the ones sitting on the nukes.
LOL. Really, you have less to worry about than if he would be in the Army or Marines. Depending on what he scored on the ASVAB, the Navy isn't bad.
Anything else you want to know, just ask! We are Air Force, so not everything is exactly the same, but most of it is quite similar. And if you just want to talk to another wife going through some of the same things, just PM me!