Some VERY good advice given already.
I owned multiple (5) food franchise locations for several years. I bought them one at a time and they were in bad shape losing thousands a month for multiple reasons. I spent a couple years going through them, implementing new procedures to "make them right" as I called it. They all became profitable and I started selling them off.
I worked my ass off 7 days a week at each location in order to accomplish this......no such thing as a 40 hour week..........
In the end did I have success, yes....
Do I consider myself lucky for having success....Yes!
Did I learn a lot about business in general, what to do and what NOT to do....Yes!
Was it worth it considering the ROI.......HELL NO! I'll never get back the time I spent......
My advice is this... If this is something you are deeply passionate about, like you get butterflies and shit every morning thinking about this being your career the rest of your life, then great! Go for it! but if you are going into a "franchise" thinking you are gonna have multiple locations, make all this money and stop by and check in on things in the next "few" years then stop now.
Not trying to be a downer, just giving you my honest opinion based on my experience.
Best of luck in whatever you decide!