Flipping houses for quick profit was a hot topic at cocktail parties and on cable TV shows during the housing bubble.

Now it’s back: Flippers have returned to residential real estate as the housing market rebounds, thanks in no small part to substantial government support.

About 21 percent of trustee sales in the five-county San Francisco Bay Area in December went to investors rather than foreclosing lenders, up from just 5 percent in December 2008, said Sean O’Toole, CEO of ForeclosureRadar.com, a research firm in Discovery Bay, California.

These investors are taking advantage of attractively priced foreclosures, historically low mortgage rates, generous home-buyer tax credits, and heaps of taxpayer dollars pouring into the mortgage market.

No wonder existing home sales recently hit a three-year high, with distressed property (a.k.a. foreclosed homes) accounting for a third of the home sales in the Bay Area and across the nation.

But today’s flippers say fixing up a property is essential to making a profit. That might be all new fixtures and a coat of paint or more serious remodeling. The days of flippers’ banking solely on a rising real estate market are history.

“We earn every penny,” said Michael LaOrange, a San Francisco resident who has profitably bought and sold two homes in Santa Rosa in 2009 and is now looking for a third property.

Investors’ growing interest in real estate is another sign of the housing market’s rebound that kept real estate professionals unusually busy during the holidays.

“This was the busiest Christmas I have ever experienced. I sold more homes in 2009 than in any other year of my 17 years in real estate,” said Christopher Stafford, a broker associate at Paragon Real Estate Group in San Francisco. He’s sold bank-owned homes in San Francisco and the East Bay, including a million-dollar home in Danville, California, that had been trashed before going back to the bank.

There’s so much property held or heading into the hands of lenders that some real estate agents dub it “ghost inventory” as they wait for it to come to market.

The prospects of more foreclosed homes hitting the market could be good news for LaOrange and others who see opportunity amid the housing woes.

LaOrange and his partner, Steven Burris, turned to real estate after Burris was laid off amid the 2008 financial meltdown and LaOrange had trouble finding work as an accountant.

It didn’t hurt that LaOrange’s mother, Kay LaOrange, had recently come into a tidy windfall. She’s providing the capital for the all-cash offers.

The two made about $25,000 on their first property. On their second house, located in a more desirable part of Santa Rosa, the two men purchased it for $205,000, fixed it up, and listed it for $239,000. It sold five days later for $275,000.