Be prepared to deal with the small things that will nickel and dime you to death. Such as using the $25/gallon paint which is Gray-Blend #345-563, rather than misty gray, just because it is the "approved" color for all facilities. We deal with goofey things like that all the time. Depending on the franchise, they will likely dictate where you purchase your supplies, such as forms, contracts, etc... Often at exaggerated prices which are designed to increase the parent company profit. I know a gentleman who owned 3 Jersey Mike's sandwhich chops and was forced out of the business when they introduced a new menu item, or cooking item. all stores had a set time to upgrade their oven or whatever, at a cost of $xxx. He could not afford, and went bankrupt. Prior to that happening, he was looking to expand. Perhaps he was already in trouble, financially, and this just put him over the edge. I don't know. But it happened, and he was managing a good sized company prior to that, so I know he was not a dunce.
I work in a franchised company. We are a very successful one. One of the negatives for us, is the other franhisees drag us down. That is something to consider, as well. Your local franchise can only be as good as the others, nationwide. Because people will remember dealing with others within your company that are owned by other companies. That may not be an issue in the medical field, and if you are dealing with local customers. It is for us, though.
I am not suggesting not going the franchise route, just telling some things to look out for, that I have seen.