Anybody beginning or extending a venture that will consume significant resources of money, energy or time and that's expected to return a profit should take the time to draft some kind of business plan.

But there are many reasons to write a business plan, including the following five:

1. You want to start a business.

The classic business plan writer is an entrepreneur seeking funds to help start a new venture. Many great companies had their starts in the form of a plan that was used to convince investors to put up the capital necessary to get them under way.