To open a 61 school all you need is CFI experience and some business knowledge. Rent an office, lease some airplanes, hire some instructors (and maybe a mechanic) and off you go.
To open a 141 school you will first probably need to get established as a 61 school. I think the FAA likes to see a couple years of history before they entertain a 141 application. You will also need a key player on staff who has been formerly certified as a 141 chief pilot or assistant chief pilot.