A WSJ article on $12/28/2015$ urged millennials to ditch their parents$$ homes and buy their own homes now$\mathrm{.}1$ It argues: $$if$,$ for instance, $30-$year mortgage rates rise by one percentage point a year from now and home prices rise by another $5\%,$ a monthly mortgage payment could jump by around $18\%.$ Can you verify this statement? Assume the house price is $$500,000$ and the $30-$year mortgage rate is $4\%($APR$)$ at the end of $2015.$ What$$s the monthly mortgage payment? If you defer the purchase to the end of $2016,$ what$$s the new monthly mortgage payment $($when the house price increases by $5\%$ and the $30-$year mortgage rate becomes $5\%)?$