http://www.soundbrew.com/small.html
THE MINI-MICRO-, PICO- AND NANO- BREWING SYSTEMS PAGE
They have a good writeup on the business impact of Brewery size. If you are going Pro, you need to be able to address the points they make.
Really good stuff here, but I guess I'd beg to differ about their contention that you're doomed if your brew system is less than 10BBL. Been to a lot of nanos lately, who have systems as small as 2BBLs, and while I'm sure they're not getting rich, they are growing. There are two I know of that started with small systems, and are now expanding to larger brew houses after making small profits for three years on their 3BBL systems. I would think that investing small to start makes it a less risky proposition too, just as long as you have a strategic plan for growth.
All that being said, saying that starting with a larger system (e.g., 15BBL) I feel is good advice when you consider that brewing is totally scalable (i.e., it takes the same labor to brew 15 barrels as it does 2 barrels). I know, sounds like I'm arguing both sides. But my main point was to say how there are definitely 2BBL operations out there who are managing to succeed and grow without forcing their owners to slave in front of their kettles 19 hours a day/7 days a week.