Kettlebells are not the answer for your situation neither are Bob Harper, JM or Tony Horton all are only in the business of selling things regardless of if they are qualified on the topic or not. Investing in a decent set of resistance bands will give you all you need for a comprehensive workout. You can get an inexpensive starter set at Walmart for $15 which includes three different strength bands, attaching handles, a door anchor and a DVD. A more upscale site for resistance bands is www.LifeLineUSA.com
where you can find complete home gyms based on resistance band training. Check out the Spark team Resistance Band and Bodyweight Training for more information and ideas.