In the Army (this is pretty much the same throughout all branches), starting out, you make around $20,000 a year base pay. You are guaranteed raises at every new year mark and every other year in service mark. I have been in for almost 5 years and my salary is roughly $27,000 a year base pay.
This may seem horribly low compared to the civilian sector but the benefits in the Army don’t even come close. First of all, you get to eat at the Chow Hall (Galley is the Navy equivalent) for free unless you have special circumstance, in which case, the Army will pay you $300 extra a month for sustenance. Second, health and dental are 100% covered. I got my wisdom teeth pulled in the Army and it didn’t cost me a cent. Third, the Army pays for your room and board whether that’s an apartment style room in the barracks, or a small house on post or, in some cases (like if you’re married), they’ll pay for you to buy a house or lease an apartment off post. There are quite a few other perks that the civilian sector can’t match (insanely low life insurance, reduced supermarket prices, etc.)
If you’re single in the military and aren’t saving at least $400 a month, either you’re doing something wrong or you’re a complete retard with your money (which is 75% of the military). Being married in the military though, it’s pretty tough to get by without your spouse working as well, especially if you decide to poop out some kids.