When I think of startup costs I think of it in terms of the IRS definition, which is the total of expenses and fees paid before you officially register your business. The most common startup costs are the fees associated with registering your business in your state, but it can also include such things as market research expenses. (For 2010 the maximum you can deduct in startup costs is $10,000.)
But I'm not sure itemizing startup costs (under the above definition) is super critical in terms of looking for investment, since in most cases it's a negligible amount. Could it be that you are really more interested in initial business expenses? For example, domain registration, web hosting, website design, etc.
In terms of business expenses, you mentioned the big ones in your comment. Other items you may want to add to your list include:
- Merchant account and payment gateway fees
- Training (books, courses, conferences)
- Professional services (accountant, bookkeepper, attorney, web design)
Also, as WSMM mentioned, add another 15% or so to your estimates to account for unexpected issues, because they will come up.
Hope that helps.