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Previous spreadsheet

This financial utility models hypothetical real estate transactions. It replaces a spreadsheet which made similar calculations.

I needed to model purchases of different properties quickly and with a minimum of clutter. After originally making these calculations in a spreadsheet, I realized how much prettier and simpler a small specialized web application could be. With control over around a dozen parameters, users with a basic understanding of mortgage finance would be able test their real estate hypotheses. My goal was to introduce them to the model through economically presented defaults. Only two actions are available to the user, who upon opening the page immediately sees a plausible model and can begin tweaking it.

The model works for any combination of home and investment property, in any currency. For every set of parameters, major attributes are graphed as they change in time, and important statistics are listed. The single interface screen reinforces the mathematical links between the input and output figures. The graph shows trends; statistics appear when relevant; both are physically small enough to coexist with the input fields. I made some explicit assumptions in the interest of simplicity: occupancy rate is fixed at 90% of the time and purchase fees at 3% of the purchase price. Documentation, besides this overview, is provided through inline links to Wikipedia articles. Some users might prefer a manual; I had one request for a flowchart showing which variables affected which output figures. Publishing the calculations would certainly increase the results' credibility.

The most significant change I am considering for this system is the incorporation of currency inflation. A constant historical rate of inflation would make the income measures more accurate over the long term.