House flipping is back.

A popular phenomenon during the housing boom, flipping is when a house is bought and sold within a six-month period. Flippers are real estate investors who buy houses, fix them up quickly and then resell them, making money off the renovation. In parts of California, it's happening at some of the fastest rates in a decade.

At a recent open house in Glassell Park, a neighborhood in northeast Los Angeles, curious buyers and neighbors streamed into a green stucco house that had just come onto the market.

The multilevel property, built in 1979, is fashioned into a hillside. It has new windows and hardware, a freshly poured concrete driveway and tidy new landscaping. The renovations continue into the house, which has new floors, fresh paint and a redesigned kitchen with upgraded stainless steel appliances and trendy tile.

Michael Delacruz is one of the real estate investors from Dossier Capital, the group hoping to sell this house. He says it was purchased a few months ago in a short sale. Records show Dossier Capital bought it for $390,000. It's now listed for more than $720,000.

The key for investors, or flippers, is speed. Their success depends on buying low and selling high, and quickly. Dossier targets up-and-coming neighborhoods and has real estate agents looking for distressed properties they can fix up and flip. They've done quite well.

"Typically, our houses are in escrow first week," Delacruz says, "maybe even the first day that it's listed."

The demand can be intense. Houses are getting multiple offers, sometimes five or six the first day they are put on the market. Part of the reason is pent-up demand. Another key factor is a limited supply of houses, and thus ensues a frenzy.

"First of all, most of the foreclosure crisis is behind us, so there are far fewer foreclosed homes now on the market waiting to be sold," says Jed Kolko, chief economist for the real estate website Trulia.

Another factor, Kolko says, is that construction is still recovering and new homes are not going up as fast as they once did. In addition, though prices are rising, many people are still underwater — they owe more on their houses than the market says the homes are worth.

Those who can sell their homes and live in up-and-coming neighborhoods, like Glassell Park, are in a good position, Kolko says.

"It's a seller's market; houses are going for above asking prices," he says. "We're seeing homes spend less time on market before they sell. ... Prices are still relatively low, and mortgage rates, of course, are very low."

For buyers, however, this can be frustrating.

Connie Molina came through the open house in Glassell Park with her husband. They've recently started looking for a house.

"We'll see a house, and then ... within a week, it's already sold," she says. "It's gone."

According to DataQuick, a company that analyzes real estate trends, flipping is up in some parts of Southern California by as much as 45 percent over last year. And in April, the region reached a milestone: Home sales hit their fastest pace in seven years.

Both economists and investors agree that as long as mortgage rates stay low and the economy keeps growing, this housing recovery will continue.

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