It is incumbent on you to thoroughly research all aspects of the industry you are considering prior to making an irreversible investment. The risks are high. Your failure could well result in the loss of your investment (as well as any other property you may have pledged), your marriage (to the extent that your spouse was not equally committed to franchising and the inherent risks involved), and, possibly most important, your self-esteem. Contrary to much of the hype surrounding the industry, there are no guarantees. To think that you can simply pay a franchise fee and automatically step into a guaranteed money machine is naive at best, and financially fatal at worst. There is absolutely no substitute for extensive investigation.
In addition to fully understanding the FDD of a franchise system that you are thinking of investing in, the savvy prospective franchisee should also be well-versed on the operations of the primary competitors in that field. Research is a tedious, boring process, but doing it carefully and thoroughly can greatly reduce your risk and exposure. The benefits of this research will be immeasurable. After you have determined which franchise system holds your interest, request information from all of the companies that participate in that industry. The incremental cost of mailing (or calling) an additional 15 or 20 companies for information is insignificant in the big picture.
The burden is on you to ensure that the choice is fully researched. Only you can maximize the likelihood of success and minimize the chances of failure or unfulfilled expectations. Take full advantage of the tools available to you. Do your homework.