I think it really depends on what you want from it. I have had plans to open a nano for a few years now but I am starting to re-think it. If you are going to open a brewery to make money...much better and easier ways to do that! Obviously we all love to make beer. I think the deal killer, or at least a big disadvantage, is all the BS that goes along with a brewery. Licensing, permits, taxes, payroll, etc..pretty much takes a lot of the "fun" out of it for me. I really just enjoy seeing people enjoy my beer. So I brew a lot of beer and give it away at tastings, beer festivals, etc. The cool part is that I sell shirts which covers the cost of the beer and I actually make a little bit of money. If you are still set on the nanobrewery idea you might want to read this...
http://www.probrewer.com/vbulletin/showthread.php?t=24441