Perhaps I'm wrong.
One of my best experiences was with a personal trainer -- James -- in Tampa. He made me realize through plyometrics and other exercises that developed explosive strength -- you don't need much beyond your body weight and some simple tools. It doesn't take a gym membership.
Now, the American College of Sports Medicine's Health & Fitness Journal says you can get a complete workout using only body weight, a chair and a wall. The workout includes a wall sit, push-ups, crunches, squats, lunges, triceps dip, planks, and more.
Take a look at this article. It makes sense. One thing is missing -- the chinup. So perhaps I would add a lucky 13th exercise to this list.