In order to start a web based business do you need to know everything about it and why?

Here is an explanation of web based business:

http://en.wikipedia.org/wiki/Electronic_business

Example:

Web site for selling second hand personal computers.

Do you need to have studied and worked for 5 to 10 years in order to be better in the business.

PLEASE READ HERE:

And if there is something wrong in the country about economy will this business lead to productive time spent so you will be allright overall with your work?

Or in other words will the internet last over the long term in order to have a good impact on the induvidual?