Mortgage affordability at lowest point since 2009

The typical homeowner spends 17.5% of their income on monthly mortgage payments, according to Zillow's second-quarter affordability report. That income share for the median household hit its highest point since June 2009.

Despite the nearly 10-year high, the rate still sits below the historical average from 1985 to 2000 of 21.2%. The rising disconnect stems from a discrepancy between home value growth and wage growth. Median home values in the U.S. increased 8% while median household incomes only climbed 2.8% in the past year, according to the Bureau of Labor Statistics' Consumer Expenditure Survey.

"Low mortgage rates have kept first-time homeownership and move-up homes within reach for many Americans, even as home values have soared to new heights. While mortgage rates remain low by historic standards, they are creeping upward, eating into what buyers can pay, and in a handful of pricey markets, affordability already looks unnervingly low," Aaron Terrazas, senior economist at Zillow, said in a press release.

The issue amplifies as housing value drops, making homeownership proportionally more difficult stepping lower down the income scale.

"Among lower-income buyers in those pricey markets, it is outright impossible to afford the mortgage on even a lower-priced home. As rates rise, both buyers and sellers will have to temper their expectations further," Terrazas said.

The top-five metro areas with the highest mortgage affordability rates all reside in California. San Jose stands above the rest at 53.5%, followed by Los Angeles (45%), San Francisco (44.9%), San Diego (37.9%) and Sacramento (28.8%).

Conversely, the Rust Belt boasts the cities with homeowners spending the least on mortgage payments. Pittsburgh (11.7%), Cincinnati and Indianapolis (12.5% each) led the way.