Author here. Thought I’d highlight my favorite, perhaps non-obvious feature: the slope of the charts tells you whether the variable is positively or negatively correlated with the cost of buying. And depending on the settings, that slope can change from positive to negative. For example with the defaults, the down payment chart is flat. This means the total cost of buying is relatively unaffected by the size of your…
Your mentioning of this made me check out the graphs again - and I noticed that the graph depicting the size of a down payment was flat. That could only mean one thing: the cost of mortgage insurance (that you will be forced to get if your down payment is lower than 20%) hasn't been included. That's a major cost on low down-payment house purchases. Intentional or oversight? https://en.wikipedia.org/wiki/Mortgage_insu…
The interaction between down payment rate and mortgage insurance rate also reveals a limitation of our user interface: On the one hand, it’s nice to have all the variables decoupled so that you can set and explore them independently. On the other hand, many of the variables are not independent. If you change one variable, you may need to change other variables to maintain a realistic scenario.
Having the mortgage insurance rate tightly coupled to the down payment would probably be too limiting, but maybe there’s a still a way to better identify when certain variables (or combination of variables) are unrealistic.