This is one of the most critical stages of planning as it is the starting point for all your financials. Defining what the true market opportunity is can help you decide if your business idea actually has legs or not!
Make sure you create a research document to keep all the notes and links in a safe place. Remember to cite all sources of information on your documents.
Your market opportunity document should normally be 1-2 pages long.
Your market opportunity should explain what is the problem that you are trying to solve? And what is the pain point that someone is willing to pay you to fix? What does it personally mean to your customer? Do they already have a fix and what are they paying to solve it?
What does the market segment look like? You need to quantify the number of potential customers that exist, how long has that market existed and geographical location.
Can you further segment your market to be more targeted? What are the market and segment trends?
What is the competitive landscape like? How many companies occupy the space? Is there truly scope to add another? A SWOT analysis & competitor matrix are both fairly quick ways of getting to the bottom of this.
What revenue do you think you can charge? Can you estimate how many customers would buy? What is the total potential revenue your business could make? What would make a customer buy from you?
The above will probably take you longer than you think, but it is worth the effort as you can't go past this stage without the information.