can I leave my position as director and start my own?

There is a physical therapy chain in the town I want to live in. They offer director positions to run individual clinics. Would it be bad practice to work there for a while, learn their ways, then start my own clinic in the same town and possibly franchise out or be the chief operator of a a few clinics of my own in the same town or elsewhere?
I feel like if you work somewhere, you can form relationships, and then when you leave you may form some enemies or is that just how business works.

What you describe is common. This is why they will ask you to sign a non-compete contract promising not to open your own PT clinics in the same area within a certain amount of time. (If that time is too long, a court will nullify the non-compete, but a year is easily enforceable.)