You would have the issue of public trust. Why would they want to buy slabs of meat out of the back of a van in a parking lot when they can go to the store and get it in a nice cellophane-wrapped package where they have been getting it their whole lives? If you want to try this little experiment, find a dairy farm near you and offer to buy 1 cow/bull from the farmer, and bring it to your butcher friend. See how you do. As it currently stands, it doesn't look like you can get much of a leg-up on the large processors.
Believe it or not, I have seen men sell raw meat in New York City bars. Steaks, pork chops you name it, and the customers were buying (including the bartender).