I'm far from any type of expert on this subject, other than a customer.
In my town, a local tavern owner installed a small 2bbl system. They always have three different beers of their own on tap, and usually more. They don't sell outside the tavern. They also have the best tap selection in town of other beers. They installed this about 8 years ago, and they brew four days a week. This past summer, they began constructing a production brewery a few miles away. This will be a 20bbl system when operating.