When Craig Blackmon sold his Seattle home two and a half years ago, he did what most sellers do — he contacted an agent.

As an attorney, he appreciated how complex the transaction could be. Still, there was that commission to pay — about $25,000, split between his and the buyer’s agents on the $482,000 home.

Next home he sells, he plans to go it alone.

If Blackmon follows through, he will be going against the grain. With the housing market’s sharp shift in favor of buyers, it’s clear that a real estate agent can help a seller bring in the most prospective buyers. But a new study calls into question how often using an agent will yield a higher net price, after commissions are considered.

The National Association of Realtors says its surveys across the U.S. show sellers who use a Realtor get about 16% more for their homes than the for-sale-by-owner, or FSBO, crowd.

Do Agents Sell Faster?

Recent research on the Madison, Wis., market found no price advantage. But homes marketed via Realtors and the Multiple Listing Service were more likely to sell in 60 or 90 days than those put on an FSBO Web site, according to the study, co-authored by Northwestern University economics professor Aviv Nevo.

“Some people have gardeners mow their lawn and some people do it themselves,” Nevo said.

To go it alone or use a Realtor can be a $30,000 question for the seller of a median-price home. The NAR says the number of people going solo hit 18% in 1997. But in the following boom years, the FSBO rate declined, even though selling a house seemed to require little more effort than planting a lawn sign. It hit 12% of sales nationally in 2006.

Nevo isn’t sold on NAR’s figures, but independent national data are hard to come by. In his Madison study, about a quarter of the transactions in recent years were FSBO deals, he says.

The study found that real estate agents typically brought sellers higher prices, but not enough to offset commissions. So cutting out the middleman could pay off.

That doesn’t take into account higher carrying costs due to the longer FSBO sales cycle, however. About 20% of those who listed on their own later hired a Realtor.

The data provide a shot in the arm for FSBO advocates, though Nevo cautions that he can’t say whether the findings would hold true everywhere. Madison has one of the nation’s largest for-sale-by-owner Web sites, FSBOMadison.com.

Colby Sambrotto, chief operating officer of Forsalebyowner.com, thinks more people are selling than the NAR data show. He says FSBO listings are growing but at a slower rate now that the housing market has cooled.

Some skittish would-be FSBOs could be opting to go with an agent, Sambrotto says. But the slower growth might just reflect fewer houses arriving on the market.

He thinks the do-it-yourself approach is here to stay.

“The commission structure doesn’t make a heck of a lot of sense in the modern marketplace,” Sambrotto said.

His Web site charges sellers $89 to $899. The low end gets a listing on the Web site. Upper-end packages come with more marketing bells and whistles, including listing in the same local Multiple Listing Service that Realtors use.

‘We’re All Adults’

Blackmon thinks most people can go it alone, with just a little help. After selling his own home with a Realtor, he set up his law office two years ago to specialize in representing home buyers or sellers without an agent.

“We’re all adults,” he said. “We’ve all bought and sold stuff. I think we all have an idea of how to market and sell. It’s the legal stuff people may not be that familiar with.”

But NAR spokesman Walter Maloney says would-be FSBOs should ask themselves a few questions: Do they really have the time to show their house themselves? Do they understand all the paperwork? And do they want unscreened people traipsing through their home?

Then at the bargaining table, are they comfortable negotiating against the professional who likely will represent the buyer?

“Selling a home without a real estate agent is like representing yourself in court,” he said.

These are difficult times for sellers. Sales of existing homes fell to a five-year low in July, according to NAR data, and the glut of unsold homes climbed to its highest level since 1991.

Mark Bazzetta, a Realtor who specializes in condos and cooperatives in downtown Chicago, says everybody should try to sell their own home at least once. Why not save some money? He applauds those who have the skill to pull it off.

But he knows it’s tricky, and takes time.

“I’ve had friends who have kind of thought about it,” he said. “I’ve said ‘give it a shot.’ If it doesn’t turn out the way they expect it and want it to, I’ll be there for them.”

Nevo says the Northwestern study passes no judgment on whether someone should use a Realtor.

“Seventy-five percent of people aren’t going to change their own oil,” he said. “They’re not going to sell their own house.”