Great insights from Funkapottomous. As he mentioned, the first place to start is preparing your business plan. This will require doing a lot of research and putting it down on paper.
Each State, County, and sometimes City, will have their own rules about operating a brewery. This will determine how much you can brew, where you can brew, and how you distribute. In some places, you can brew at the same property as your residence as long as it's in a separate building. Others may require a strictly commercial facility in a specified area of town. Some will even want to regulate your waste products. The regulators will probably be the toughest part of this endeavor.
Once you've determined your potential location, you need to think about equipment and storage needs. How big do you want to be to start? Will you only supply kegs to restaurants and bars or will you bottle for retail? How will you distribute the product? Will your facility allow for expansion? Can you lease time in an existing brewery? Be realistic as to location and equipment costs and pad your estimate by at least 15% for unexpected costs.
Assess the market. Go talk to your prospective clients and be sure they'd be interested in your product (be sure to talk to the people who actually have the decision making authority). What will set your product apart from their current offerings? While I was at Stone Brewing Company on Saturday, we were talking about the pure marketing genius of Greg Koch. After all, the American beer palate is really based more on marketing than taste, and a good marketing plan could make or break you.
All of this will determine your capital needs, and to some extent the potential ROI. Now you know how much money you'll need, it's time to go raise some capital. This is harder than you might think, but you have to be persistent. You have to really want it, and you have to know some people with money. I was suprised to see that Forest Rogness' (from AHS) attempt at a kickstarter campaign for a brewery didn't succeed, because he is somewhat known in beer circles. I think it was probably that he lacked something in the marketing end. But, if you've got a strong business plan and a strong marketing plan, money sources are out there.
Finally, if you don't feel you have the ability to write these plans, you might try to hook up with some grad students at the local university, maybe someone will take it on as a thesis or project.
Good Luck, you've got your work cut out for you!