Answer:
There are No real licenses per say bu8t a business licence may be a good star6t depending on where you plan on practicing. Now best to check with licencing in your city and state.
There are suggested ways to becoming a "Pro" trained Dom but you must find someone who is also reputable established and willing to take you under their wing. Along with proper CPR and first aid training highly recommended since as we all know things can sometimes happen. BE prepared and above all SAFETY FIRST.
FOLLOW PROTOCOL , (PROMOTE AND ADVOCATE SAFETY AND AWARENESS)