A reputable profesional business plan writer would not undermine your idea. That being said, in my experience, I have found it helpful to have whoever you hire to work on the business plan sign a non-disclosure agreement. A really helpful book for budding entrepreneurs is The Art of the Start by Guy Kawasaki. This book will help you formulate your idea and your pitch. If you want to try writing your own business plan there are some good books out there. There is also software called Business Plan Pro. As far as your invention, you can at least do a preliminary patent search first yourself to at least get an idea if it is original. I would then have a professional do a full blown search. If you have an invention that you think is patentable, it is probably a good idea to file it as soon as possible. You should find a good patent attorney or agent that is familiar with the field of technology of your invention. Good luck with it!
For a professional to help you with a business (not buisness) plan, they will need a clear understanding (not undermining) of what you want. You can t present an idea to him that is misspelled, poorly punctuated, or written with little thought, and expect him to respect your plan ideas.
