By all means a business needs a business plan. It's how you organize your organizations and communicate what your intentions are, the scope of your work, and what success looks like for your efforts. Business plans also can stop you from making mistakes that could doom the success of your business - like failing to pay yourself, or taking too much money out of the business for personal expenses.
Your business plan should grow and change with your business. Nothing is carved in stone.
A business plan demonstrates financial literacy and competency. It demonstrates that you understand where money needs to go, and how to project income. How can you expect anyone to lend you money or extend credit if you can't demonstrate adequate planning skills and money management?
