There are a number of ways to make a new business plan. Here are four of the options:
This takes an enormous amount of time. As well, working without input from experts will not improve your business strategy and writing. Writing the plan yourself from scratch can give you product control if that is your fear and it will cost less.
Starting with a business plan template can give you input for the content and guide you through the process. This can make you feel better in knowing exactly what it is funders are looking for in a plan. Templates are usually cheap (under $100) and have financial models in Excel and other programs which will help save you time. However, you will still need to tailor the template to your own needs and put in the time required for all your research.
A business plan writer can take interview info, notes and bullet points from you and put together a plan. This will save you time but it will obviously cost.
This person can write the plan from scratch or just give you comments and advice. They will know what funders are looking for and how to raise funding and operate efficiently. Bringing in a consultant will inflate your price, but may prove to be invaluable if they're able to keep you away from common business plan pitfalls.
Those consultants from an experienced firm will have more resources and knowledge to guide you. You may also get lower rates because of their connections. Using a business plan consulting firm is definitely worth it if you have the money to put down.