Anyone own a franchise or fast food restaurant?

My inlaws want to go into business with my husband and get a fast food franchise, either to buy or be a franchisee. They have more than enough liquid assets for pretty much any company but does anyone have any experience in actually owning one or franchising?? Basically any you would suggest to avoid or that are great to go in to? We are in the pacific northwest and the only thing near us is a subway. They used to be in diner style restaurants and me and my husband both worked for a long time in parts of our lives in various food places so we do have experience working and managing just not owning. We are doing research ourselves but figured we exhaust all avenues and I would ask here too.