Is there a gym between your house and your work? Or at least one that is not a big detour? If so, I would suggest joining it and going in the morning before work. Do a mix of weight training and cardio. For cardio, mix it up with elliptical, walking on a treadmill at a steep angle, running on the treadmill, summit climber/stair climber, stationary bicycle. Do a different one of those each time you go, or mix it up further by doing 8 minutes on four different machines. For the weight training, start off with some simple lifts and progress from there. Do the weights Mon, Wed, Fri and the cardio Tue, Thur. Assuming you work 5 or at worst 6 days a week, also do some outside cardio on the weekends. Are there any bike paths near where you live?