Renting vs Buying

It's a national concern."

Rents increased faster than home values in 20 of the 35 largest markets.

But even as rents climb, there is still strong demand for rentals, creating a housing crunch in some cities.

"Places hard hit like Seattle, San Francisco and Denver are having a hard time keeping up and building enough units to satisfy demand," said Gudell.

Renters in San Francisco face a nearly 15% rise in payments while rents in Denver went up 11.6% in April from last year, according to Zillow's Rent Index. Only two cities on the list experienced a drop in rent from last year: Chicago and Minneapolis.

Low mortgage rates make home buying an attractive option, but large rent checks can make saving for a down payment tough. On a national level, homeowners can pay an average of 15.3% of their income on mortgage payments each month, the report found, while renters will dish out roughly 30% on rent. Gudell said tenants in high-income areas can expect to pay closer to 50% of their income on rents.

"There are bunch of things keeping renters on the sidelines and that means usually the folks that would be normally making the switch to become homeowners are still taking up the rental units."

Here's how much rent prices rose in the largest markets in the country in April from last year, according to Zillow's Rent Index:

San Francisco, 14.9%

San Jose, 12.9%

Denver, 11.6%

Kansas City, Mo., 9.5%

Portland, Ore., 8.6%

Charlotte, N.C., 6.6%

Austin, Texas, 6.2%

Cincinnati, Ohio, 6.2%

Seattle, 6.2%

Houston, 6.1%

Detroit, 6.0%

Sacramento, 5.9%

Los Angeles, 5.6%

Dallas-Fort Worth, 5.5%

Phoenix, 5.4%

Boston, 5.2%

San Diego, 5.1%

Atlanta, 4.9%

San Antonio, Texas, 4.6%

St. Louis, 4.5%

Pittsburgh, 4.4%

Riverside, Calif. 4.2%

Tampa, Fla., 4.1%

New York, 3.4%

Miami-Fort Lauderdale, 3.2%

Philadelphia, 2.8%

Baltimore, 2.7%

Columbus, Ohio, 2.6%

Cleveland, Ohio, 2.4%

Las Vegas, 2.1%

Washington, D.C., 2.1%

Orlando, 2.0%

Indianapolis, 1.5%

Minneapolis-St. Paul, -0.3%

Chicago, -1.0%