Median home values (August 2018): zillow.com/data
Mortgage rates: zillow.com/mortgage-calculator
Interest rates: The live market rates from the Zillow Mortgage Calculator
The amount spent on housing is 30% of the total income as industry experts recommend.
Tools used to make the viz: PHP GD Library + GIMP
For more information about the methodology and for an additional graph of median home values, check the original article.