Generally speaking you don’t, because the job of the franchisor is to turn you into a successful business owner through operating their proven system. They shouldn’t just train you ‘how to run the store’ they should also train you ‘how to run a business’. That should include how to do a business plan, how to manage your finances, how to market yourself and how to engage and manage staff.
Having said that, experience of running a business, even if it was someone else’s, will of course shorten the learning curve and will bring with it useful knowledge of what has and hasn’t worked for you in the past. It certainly won’t be a disadvantage, although many franchisors would prefer not to take someone who has worked in their actual business sector as they may bring bad habits with them.
Conversely, there is an increasing trend for existing franchisees to become both multi-unit franchisees for the same franchisor and in some cases multi-brand franchisees for two or more franchisors. A good food service operator is a good food service operator so, provided they have the right management team, this can be a great advantage for both franchisor and franchisee.
Don’t worry about your previous business experience; there are opportunities in franchising for people with all sorts of backgrounds. Different franchisors look for different levels of experience in different areas. They like to see evidence of success in something but what matters more is your ambition, your potential and your ability for further success in the future.