The most important factor to consider when starting to build a business is the target audience. You have to think of who would you want to cater to. Who are the communities that you may profit off of. Like for example if there is a school near you, you should know that students would be your target audience. You should start a business where students can buy materials from or a place they can study or even hang out around. I believe that if you studied your target audience, the first step of your business is already successful enough.
There are so many criteria to consider before starting up a business, and I think this one that you mentioned is a very essential part, but there are cases where people who are business minded would prefer to start up a business that they are passionate about, but this time around, they will have to go in search of their own audience/buyers, rather than actually offering services that they think most people around would be comfortable with.
I feel the main thing is to keep having passion to continuing that business. Your audience shouldn't basically determine the service you offer, but the services you choose to offer should determine the audience you chase after. And one thing that I feel most business owners don't know is the idea of keeping good business relationships. Every single customers that uses your service needs to enjoy it to the fullest. I'm actually saying this not because I'm a business person per say, but because I keep having good reasons to go back to those that has once offered me good services, and I believe so many of us here do the same.