You don't want to just ask for the "exact" (e.g. estimated ) cost of a rehab project. Often costs will increase due higher material costs, unexpected repairs, and time delays. The professor's rule of thumb is to add an additional 10% for minor rehab (<= $5,000), and higher percentages as the rehab becomes more extensive.
The professor as created a useful algorithm for this in his Deal Evaluation Tool. This is an excel spreadsheet you can use to generate all your financial information for you and your investors for any type of real estate deal. You can check it out at: