This question is understandable. whatever firm you wish to start, it is quite likely to change with the passage of time as new opportunities arise and are explored.
Success stories include people who stuck to a field they knew, as well as those who broke away into something completely novel. What i can say is this - take time to investigate every aspect of the business before committing yourself.
There is a story about a couple who went on early retirement because of the husband's health. they took a big loan and sank their savings into a restuarant. Only once they had started did they realize it required from each of them 16hrs a day, six days a week to run.
However, it is possible to come to a decision. Try the following starting points if you have not already decided what to do:
。acquire knowledge of an industry, sport or game and seek ways to supply others with that interest profitably;
。look at stuff for sale on eBay and grab the opportunity of selling almost anything on there;
。get a job in a small or medium-sized enterprise and learn how they operate.
Remember also that, it is worth forming a relationship with a business adviser so as to have someone to positively bounce your ideas off. This must be someone with a fine balance of imagination and realism as well as experience outside a narrow professional field:)