Can girlfriend live with me when I get stationed?

Your unit will require you to maintain a room in the barracks and some units will even require that you are in your room for inspections and such. But you can maintain an apartment off base as well. Though if you get in trouble for missing formations your unit may restrict you to the barracks without any concern for you having an "unauthorized" apartment off base. You should also remember that you will not be receiving housing allowance while you are doing this. That means you will be out of pocket more money than you can likely afford. You can see that you and your girlfriend would be miserable sitting in a tiny apartment without money to do anything. That sounds harsh, but you need to consider the worst case scenario. Hope that was a better explanation than your recruiter.