Studios vary greatly in size, scope and equipment. From your passport photo shooters (ok, barely a 'studio') to indoor setups big enough for vehicles. Rental, manpower, equipment, fixed costs, expendables, etc -- a large number of things you need to take into account.
I think you'd get better response posting this in The Photo Biz section where a number of working pros have shared their knowledge and experience (better close this thread first though - not nice to cross-post!)