Across a large swath of Southern California, owning a house has become less  attractive financially in the wake of rapid home price gains last year,  according to a new study.

The mortgage payment on a median-priced, three-bedroom would exceed the rent  on a comparable property in Los Angeles, Orange and Ventura counties, according  to a RealtyTrac analysis released Thursday, based on prices from the fourth  quarter of 2013.

Nationwide, there were only 29 large counties in that situation, including  the Northern California counties of Santa Clara, Alameda and San Francisco. A  year earlier, nowhere in Southern California was rent cheaper than monthly house  payments.

In Los Angeles County, RealtyTrac reported, the monthly house payment for a  median-priced three-bedroom was $1,987 — about $100 more expensive than fair  market rent for a similar property, as calculated by the U.S. Department of  Housing and Urban Development.

A year earlier, house payments were about $500 a month cheaper than rent.

The median price for a three-bedroom L.A. County house was $417,333 in the  fourth quarter. The monthly house payment for such a home rose 40% compared with  the fourth quarter of 2012.

To qualify to purchase such a house, a buyer would now need to make at least  $95,389 annually, according to RealtyTrac. That’s about $42,000 more than the  median-household income and $27,000 more than the income needed to buy the  median house a year earlier.

The widening disparity between rent and home prices underscores a growing  affordability crunch across the region. Real estate experts say the high costs,  without corresponding income growth, have depressed sales