My plan for staying in shape... walk.
We're all too busy to work out on a daily business or can't afford a gym membership. The good news is... you don't need to.
I stay in a lot of hotels. (Free workout facilities by the way). Most times I take the elevator up and down twice. Up with bags and back down when I check out. The rest of the time I'm riding the stairs. Doesn't take much time, zero cost, but lots to show in terms of exercise.
I bet there are a lot of things in your life that you could count as exercise. Mowing the lawn, shoveling the driveway (unless you live in the South), walking to the store or riding a bike, etc. If you have more ideas, send me an email.