You really can't go vehicle specific in training at the beginning. Get your overall tech understanding of the mechanicals as well as electricals as a lot of vehicles are 'computerized'. Then in time, you can specialize in what you want.
Transportation is going to be going different ways all over the place in the next several years. It will be hard to figure the way to go. Over-the-road trucks, diesel running trains (generators), heavy equipment, consumer vehicles, recreational vehicles (ATVs, side-by-sides), boats, helicopters, small planes, etc. are all changing based on supply and demand of fuel, equipment, availability, recreational, weather, etc.
Now, you wanting to wrench yourself and run the business? That is a lot of hours, customer service, parts ordering/logistics, pricing, building maintenance, costs, tools, and it is a really big job to handle. Get yourself taught with the best way of getting a job in the industry, learn the setup for the business, then look at opening a full shop. You may have to work out of your garage at first. Look at what the schools offer, where do their grads go to work, etc. Pick your best option and go strong.