The REI Partner™ Cash Flow Analysis Component provides invaluable assistance when evaluating a potential deal for future cash flow.  With REI Partner™, you enter data about the property such as purchase price, closing costs, expected expenses, vacancy rate, gross income, property management fees, etc.  Also enter sources of funding: mortgages, out-of-pocket, etc.  The program then generates a spreadsheet-like grid that will detail everything from cashflow analysis to ROI to NOI to CAP rate to GRM.  As mentioned earlier, users can also choose to apply the "50% rule" or define their own criteria for taking unforseen expenses into account.  A "What-If" feature allows users to make changes to the criteria once results are generated and immediately see how those changes effect your cashflow. Several valuation concepts known only to experienced residential real estate investors are implemented in REI Partner™, such as the 50% rule, 2% rule, etc.

And of course you can print your results and take them with you.