Well it really depends on the state and local laws. When my hobby turned into a small business a lot changed.
First off consistency. You have to be sure you are brewing the same beer each time or consumers will be disappointed and unimpressed.
You will need to obtain an ABC license to not only sell beer, but call yourself a micro, nano, or brew pub.
You will need to provide exact gravity and declare exactly what abv your beer is so the government knows what you are selling, and they can tax you appropriately.
You will also need to check local laws and regs to ensure you are legally allowed to serve or sell beer in your establishment above a certain gravity. Some states do not allow beer to be sold at all that is over 8% abv. Others require you to purchase such beers at a state liquor store. Others have no stipulations. You also need to ensure you are not breaking any contracts with other breweries (the big 3 are big on this) saying you can only serve their beer in your establishment or they can sue you.
Luckily I live in CA and while it is the least small business friendly state in the union, the beer laws are pretty lax. That explains the over 300 craft breweries in this state. Other states while they may be more friendly to small businesses are less beer friendly. All we have to do is look at some of the ridiculous homebrew laws still on the books in some states. AL still has a ban on homebrewing last I checked, but the AHA and BHA is fighting this very hard.
If this is something you are serious about check with a local business attorney about the prep work, fees, taxes, and licenses. From there you will have to start setting up your brew house. Start shopping for equipment from breweries that are going out of business or are upgrading. Usually nano breweries start on a 10 bbl system. You will need to look into hiring assistant brewers and lab techs as well to conduct yeast and water analysis. All the research I've done shows no state allows you to sell "homebrew." while the pilot batches can be done at home on my 1100, the beer to be sold must be brewed on FDA approved equipment in government approved locals.
Be warned that I have never met anyone who started a brewery to become rich. After you've paid your staff, your distributors, suppliers, and taxes, plus the 16 hour long brew days 3-4 days a week you pay yourself just over minimum wage.
If experience and professional beer is your goal I recommend becoming an intern at a local craft brewery to see if this is something you really want to do. Pro brewing is not homebrewing, and many other factors come into play. Home brewers have much more freedom than pro brewers. There is an old saying here in the craft beer world, "if you've worked at san Francisco brewing company for two years and you still want to brew it is in your heart." the equipment and environment is much different. If you want to intern at a brewery don't expect to get paid in money, but rather knowledge. I have a mashtun that needs shoveling if this is the route you choose to go.
If starting from scratch is really the risk you want to take then you need to think about where the money will come from to setup shop. You need fermentation chambers, a brewing system, labs, brite tanks, packaging equipment, and of course someplace to put all this stuff. Then uncle Sam comes in to traipse through your brew house and make sure it's up to code. After that the government gets their taste. Here in CA a six pack of craft beer is about 8.00 and 25% of that is taxes. It's not just the consumer pays taxes by the way.
