I am trying to figure a budget for house flipping. My first consideration is “What will my mortgage payment become each time I buy one or more houses?” Thanks to JohnSUN and his help on the question at How Many Houses Will I Sell Each Month?, I can project a rather even workload for the year.

However, I would like to be able to project some cash flow needs to the mortgage company using the same workload methodology. I have set up a spreadsheet, which is shown below, with the formula for distributing purchases shown in the formula bar.

How can I dynamically (using a formula of course) calculate the new mortgage payment, interest payment, and of course, the principal reduction each month?