I don't want to sound like an ass, but why are you having a baby when you're obviously not financially stable?
The military is a decent option, but you'd have to be married, and don't you fear him going off to Iraq or Afghanistan? After boot camp, you can probably live on the base with subsidized housing.
Here's some info about Army benefits:
https://www.goarmy.com/benefits/soldier_and_family.jsp