Home Gym: buy a cheap but sturdy squat rack for pullups, hang some gymnastics rings on them, and get an ab wheel. Work up to 20 pullups in a row (max number of pullups for the marine corps pft) and work towards advanced calisthenics moves like ring muscle ups, front/back lever, one arm pullup, planche, freestanding handstand pushups, etc. You can gain some serious strength (and size, though not as much as weights) with calisthenics. Just look at all they professional gymnasts out there. Jump rope is a great option for cardio and its easy on your joints. Weighted/high rep pistol squats, hill /stair sprints, and kettlebell swings are great for your lower body.