Get your hands on some good entrepreneur's manuals (at the bookstore or the library) and continue your research on the web. There's a ton of information out there--especially relating to startups--in a range of different industries. Many costs are similar, and you can get a good idea of what to benchmark.
Realize, though, that costs always run more in a startup than projected. Your project would benefit by showing what that percentage is for the industry (20 percent, 30 percent, 50 percent), so you can better show how cash flow will vary as your proposed "business" gets off the ground.
All the best,
Brad Sugars is the founder and chairman of ActionCOACH. As an entrepreneur, author and business coach, he has owned and operated more than two dozen companies including his main company, ActionCOACH, which has more than 1,000 offices in 34 countries.