At the end of it all, hiring small business consultants would be the key to your company's overall success. You want your business to be the best that it can be. For this to happen, long-term and short-term goals must be set and these changes must be implemented in a timely manner. With this in mind, you may want to involve the business plan consultant in daily operations.
You may find that the easiest part is the actual writing of the plan. The real work comes in the data-gathering, which may take you a hundred hours or more, depending on what you already know or have researched. If your new venture is in an area where you've been working, you may already know about your customers, your suppliers, your marketing plan, your organizational structure, your financial and cash flow needs, equipment, inventory, and so on.
While these are easily available online, some of them are way better than the others. A lot depends on the approach that goes into writing the business plan.
U.S. Census Bureau (census.gov): A source for a variety of useful statistics, especially the Economic Census that comes out every 5 years.
business plan database
business plan canvas
business plan basics