A couple of excellent sites where you can find business plans as well as other information are
http://www.sba.gov/ and
http://www.score.org/index.html since they are designed specifically for helping businesses to start and operate.
However, depending on what the business is, we might be able to help you here. Someone here might be in the very same business that you want to start. What is the type of business that you want to start, please?