What's my best bet for getting all the information I need for a simple business plan?

I have someone who is interested in one of my ideas. They want me to find out about what I’ll need to get the ball rolling, and what the outlook is like for the business in the area if I’d be starting small.

They were even ok with me asking businesses and doing my own homework about how the market is looking, but I want to try to put something with just a tad more effort than my own sleuthing skills.

Any advice you’d like to share could probably change my life. I’ve read up on business plans, and I understand what it means to put one together. Now it’s down to demographics, and the PITCH! Hmph…