Many people starting a business have been advised to pay a visit or make a call to SCORE*, which describes itself as "Counselors to America's Small Business" SCORE is a non-profit partner of the U.S. Small Business Administration and is staffed by volunteers with extensive business backgrounds. One can get counseling online, via the phone, or in one of 364 SCORE offices throughout the United States. The advice is free to all comers.
I have heard quite a few people complain that SCORE volunteers discouraged them from proceeding with their businesses, and I confess I had similar feelings after my first visit to a SCORE office. The counselor asked me why anybody would hire me as a marketing consultant when there were so many other marketing consultants out there. (This was during the dot-com recession when many unemployed marketers were calling themselves "consultants".) I took it as a negative, but I realize now that he was asking me if I could differentiate myself from the pack. It was a fair question; I had broad marketing skills but hadn't figured out what niche I might fill.
One of the problems I see repeatedly with startups is lack of focus. Unless you have a strong patent on a product or process, chances are extremely high that there are others, perhaps many others, who are offering or will offer what you do if it shows any signs of being profitable. There is undoubtedly an equally broad field of people who are willing to buy that thing if it provides some sort of value, but how will they find you?
You simply can't hope to succeed unless you differentiate yourself in one or more ways, and that means you need to narrow your offering and positioning so potential buyers can recognize your value to them. That means you must start out with a narrow focus. Only when you have grown and are profitable should you broaden into other markets or product lines.
Listen to the SCORE counselors. Give serious thought to the questions they ask you. If you don't understand the feedback you get, ask to hear more about it. If you're still in doubt, get a second opinion. Chances are, these business veterans can help you better define your business and help you to be successful from the start.
* SCORE used to stand for, as I remember it, Service Corps of Retired Executives, however they have abandoned that usage, and you cannot find the history of the acronym anywhere on their website.