Lot of discussion has happened already. You may not start your company as of now. However, let me tell you that 85% businessmen fail in their business because they don't do any market research. Nothing stops you from doing market research while in the job. It can be off-job activity.
First you do some course on how to do market research. You do the research on the following points:
a) Who will be my customers? What is their profile? Where are they located?
b) What I need to do to attract my customers to my product or service? How can I take my product or services to them?
c) What is my product differentiation? What will be the brand pull?
d) Who are my competitors? Who is strongest? Why are they strong? You are going to benchmark against whom? Is there geographical variation among the competitors?
e) Did anyone earlier enter in this business and has anyone failed? Why did they fail?
f) Are there verdicts of supreme court or high course or any other court available related to the delivery of products or services?
g) Will there be any distributors? What is the psychology of the distributors? What will be their education background?
h) Do you know the product/service very well? Do you have passion to produce that product or deliver that service?
i) Have you decided about the quality of the product or service? Is there differentiation among "good', "very good" and "excellent" product or service?
j) What will be measures of performance of the employees that you will employ? When their performance will be "good', "very good" and "excellent"?
k) What will be your recruitment strategy to recruit the "right" staff? What research have you done of job market to get the "right" staffs?
l) Will you take help of your near and dear ones to run your business? What will be their involvement? What "immunity" will they enjoy because they are "near and dear" to you?
m) Are you aware completely the statutory requirements to run this business? Have you actually met Govt officials and obtained information from them or just relied on your company secretary or chartered accountant?
You can obtain the information on the above points while in the job. Remember information is the key in today's world. Businessmen or businesswomen fail because of lack of awareness.
All the best!