Mike,
That is good advice that Juzajedi offered you, and he is right on the money with ways to analyze, however, there are worksheets. Most investment books, I.E. "Investing for Dummies" has one, and so do most of the more technical books. So just look them up at Borders or soemthing. However, do remember this.....
Negative Cash Flow can serve a VERY useful purpose if you plan for it properly. You can have an investment that gives negative cash flow daily, if you are in the property for the equity, not the cash flow. IN that respect you need to plan carefully and know what you are getting into, and have some research on the market you are looking at to know if the ROI from the equity is enough or worth it to you to have a neg. cf property. I know many investors that it seems only buy properties like that, because they are buying on equity, not cash flow.
Anyways, just a thought, hope it helps and if you want to kow more, let me know how I can help.
Chris