First step, have several million dollars available to you. Usually in the region of $10M (which was the estimate for the NBA player Damian Lillard's Toyota dealership, by the time you find a property, build it out, initial inventory stock, etc., etc.)

Dunno, but I can tell you how my family started as I think it's really interesting.

Yugoslavia was just falling apart - the entire country went from planned limited production to open market. My family was importing cars from other countries as this started. The demand was so great, that when the truck with cars stopped on a parking lot at his home, people would come running putting their "reserved" stickers on cars. Everyday he did a trip out of the country and back. "Sold" all cars before he had a chance to step outside a truck.

This lasted for sometime, giving him enough bankroll to open car dealership. Not sure how exactly it happened, but few years later it became Ford dealership and still is.