It is nearly impossible to build a home without the blueprints, much like trying to start a business without a business plan. A good startup business plan includes the blueprints for the purpose, operation and ultimately the success. Building a business plan can (and will) expose any potential weaknesses in the ideas and will help identify points of strength as well.
During the creation of your business plan, you will have to come to terms with a variety of tough questions that you may not have thought about otherwise. These will put your product or service, your market and your plan under the microscope with the end goal of creating a thorough and strong business plan that will lead to success.