Numbers are important, but with something like a brewery, there are so many variables they can only help in a very limited way until you actually start crunching them yourself (a friend and I are currently putting together a business plan for a Brewpub, just for a sanity check on the whole thing). Doug's overall assessment is lucid and realistic from what we've been able to learn, but again, are you going Nano, larger Production Brewery, Brewpub? All have vastly different considerations not just in general setup and expertise needed. How easy will the local authorities be to work with? Who are your customers? What will your rent be?
These are all big questions leading me to not 'pursue the dream', because I have just enough age and responsibility (wife, kid, mortgage) under my belt that I am far more risk averse than I would have been ten years ago (of course, then I hadn't then stumbled into this fascinating and addicting world of brewing beer). Yes, starting a brewery on a shoestring budget can and will continue to work, but they are by far the exceptions to the rule and generally succeed because of an uncommon blend of skills, personality, hard freakin' work AND good doses of luck along the way.