Two bodies of knowledge for running and eventually selling an ABA practice: the operating compliance that changes state by state, and the sale and expansion questions that apply everywhere.
Six co-equal pillars, each resolved for your state. Start wherever the pressure is.
Before any ABA can be billed, someone has to diagnose the autism. Who is allowed to sign that diagnosis, and whether you can bring them in house, decides how your practice has to be owned. Resolved state by state, with the operative statute quoted verbatim.