No worries, you don't need a gym - or really any equipment - necessarily, when you're physically training to be a firefighter. When doing your cardio and strength-training routines, try to mimic the actual scenarios used in firefighter training. For example - instead of just running, run up and down flights of stairs, while hauling something heavy (to simulate a hose, ladder, victim, etc.). A weighted vest is also good as that will prepare you for the gear you'll eventually be wearing. You get the point. Get creative!