I am a franchise consultant and recently became informed that there are a couple of franchises that offer guarantees. While they don't refund all of your investment, I think it will help you feel more comfortable knowing you can't lose it all. Plus it shows how much they stand behind there business. Learn more at http://www.franchisesmadesimple.com/2010/04/franchises-with-a-guarantee/
Let me know if you know of any other ones with guarantees!