There's a difference (distinction) between repairs and sales. I would think that a repair business would require less space, less inventory, less overhead, less headache with manufacturers.
There's some well established bike mechanics schools. I would imagine that would be wonderful for you from a personal matter as well as for a business investment.
Near me is a bike mechanic and he went to a mechanic school and also was on the Mavic neutral support team at the Tour de France. Going to that particular mechanic school opened a lot of doors for him.