As with any business, you are presumably starting it so that you can provide yourself with income. There may be other, altruistic reasons, but at the end of the day you need to pay both the business's and your own as well. That cannot happen if you do not provide a good or service to the people and area that need it. After all, you may love to use your truck to plow snow, but your chances of landing a contract with the city of Tampa to do that may be rather slim no matter how competitive your rates.
"Is you is, or is you ain't, my con-stitch-ency?" - Homer Stokes, O Brother Where Art Thou? (2000)
In "O Brother", aside from its retelling of the epic poem "The Odyssey," there is a backdrop of a gubernatorial race in Depression-era Mississippi. Homer, the challenger to incumbent Pappy O'Donnell, traveled the lands trying to drum up support. This quote came toward the end of the movie when each candidate had everything on the line as everything was coming to a head. While certainly popular with some, Homer's policies and interests were called to question prompting him to ask this in reaction to the situation. If you want to or already do own a business, let's address this question of "constituency" proactively. It will save you a lot of time, hassle, and money!
According to the Census, which provides information for free, we can see here broadly just who lives in Erie County. From this we can better make our decisions and even narrow the statistics of our target market down further. Thinking of starting a pub in Vermilion? Let's refine the search here. Obviously we are looking at ages 21+ so in the city we have a presumed customer base of just over 3,500. We can break it down further but you have to ask yourself is this enough to run your business given the expenses you will incur for rent, insurance, employees, etc.? Or if you intend on doing something special and create/fill a niche (a highly recommended tactic by me) can you look county-wide or broader to draw in a certain percentage of others with your decor or theme?
After considering what you are selling and to whom you are selling it (manufacturers and distributors may also be able to help provide you guidance in which markets to target with their products), you should also look at the location of your business. In the movie example, each candidate pretty much got the run of Mississippi. But, their stumping still targeted only certain areas or cities. Just as only a certain constituency would support Homer over Pappy, you must identify your target market and get in front of them. "Everyone" is unacceptable. Using another business example let's say you want to sell inexpensive jewelry/fashion accessories in Huron. In addition to general population and product information we need to find where you can put your store that will be most effective.
Knowing we want to be convenient for girls 12-20 to reach (by the Sandusky Mall is an option, but note that it isn't right for all businesses!) let's use the power of the internet to make a map and pin up locations of the schools as well as other establishments that serve that demographic, which would include the parents who cart their kids around to do other shopping. Seeing those as well as the roads that serve them, we can add more layers to the map to help you get the right location to build/buy/rent. Once we have those prospects it is time for boots to hit the sidewalk and to literally scout things out. Talk to other businesses to get their opinion on the place. Or just spend some time observing who passes by, goes into shops, and would be generally exposed to your prospective business. The research and observation takes time but if done properly will immensely help your chances of success!
Your municipal offices could be of help to you here and at least speaking for Erie County, we are fortunate to not only have a Chamber of Commerce but also the Erie County Economic Development Corporation to assist you in various ways. While localized to downtown Sandusky, and perhaps you outside of the city have a similar organization, but there is the Sandusky Main Street Association, which is a part of a greater Ohio organization. There are private firms that do these kinds of studies for businesses as well, but they can be costly.
In an age of convenience when Starbucks are built on opposite corners so patrons don't have to cross the street for a cup of coffee, putting yourself in the way of your target market is crucial. You can't count on them to go out of their way to come to you in many cases. There are some other resources and studies you can reference, but don't get in hot water before finding out who "is or ain't your constituency".