The question of should you hire someone to write your business plan comes up a lot and this post, from the AsktheVC blog, gives you a very strong answer and some excellent comments as well. The truth is that the plan has to be your plan, and the best way to make it your plan is to do it yourself. There’s so much thinking and, well, planning that’s part of the process, there is just no substitute.
It’s not like a college essay or a term paper or a tax form, it’s a business plan. You’re going to live with it, right?
Anyhow, I highly recommend this post.