How many people can legally live in a one bedroom apartment?

my husband has received military orders to report to arizona he will be there for a year and if the military does not approve us to move on post with him then i am planning on making the move with my son there on my own. my husband told me that after being there so long ( hes going for ait school for 49 weeks) he may be aloud to move off base with me. since we will only be there a year and that it will only be me and my son for a good part of it i am considering only getting a one bedroom. ( my son is three if that helps) i know i will find out more when he actually arrives there and am not planning on doing anything until i know more. im just curious if anyone knows anything about how all this works or how things work in arizona