Dave Hermansen did not own a bird or a cage when he bought bird-cage.com, an online store, for $1,800 three years ago. He simply saw a Web site that was “very, very poorly done,” and begged the owners to sell it to him. He then redesigned the site, added advertising and drove up traffic. Last December, he sold it for $173,000.

Mr. Hermansen, 30, is among the latest wave of entrepreneurs who, like the day traders and real estate investors before them, are looking to make a lot of money without much effort.

They use little more than home computers and free software to buy Web sites that appeal to a small and specific niche. Then they fix up the sites with hopes of reselling them for far more than they paid.

But while their dreams are fueled by high-profile Internet deals — Condé Nast’s $25 million purchase of Wired News, People.com’s acquisition of Celebrity Baby Blog and, most recently, a deal this month between Guardian News and Media and the owner of PaidContent for a reported $30 million — these entrepreneurs have smaller ambitions for their sites. Many end up settling for just hundreds, sometimes thousands of dollars.

“Everyone with a site is saying, ‘If I can get it to the right value, I’m out,’ ” said Gene Alvarez, vice president for research at Gartner, a technology consulting firm. “I call it the burger-flipping model: You build up volume, you build a community and then you try to sell it while it’s still hot.”

Some Web sites begin as labors of love. Take Celebrity Baby Blog, which Danielle Friedland, the creator, has said she created after reeling off facts during the 2004 Golden Globes “about who was pregnant with twins or had recently given birth.” Four years later, People.com bought the Web site after it noticed an unfulfilled niche: “a very passionate community of young moms,” said Fran Hauser, president of People Digital.

Ms. Hauser said she would not comment on the sale price. Industry insiders speculate it was in the low millions.

Most flippers aim a bit lower. They troll the Internet for sites that, according to Mike Lyon, an investment banker at Arbor Advisors, are “undervalued property” — poorly designed, with little visibility on the Web.

While there is no data on how many people flip Web sites, the number of sites sold on eBay has doubled over the last three months, the company said. At SitePoint’s marketplace, a similar forum where users can auction off Web sites, sales have quadrupled in the last year, said Matt Mickiewicz, a founder of the site.

The changing economics of the Web have made it easier to find and exploit niche communities on the Internet. The Internet boom of the 1990s spawned companies like Pets.com that were Web versions of brick-and-mortar stores. They required stockpiling products and shipping them to customers. But that model came crashing down with the Web bust of 2000.

Since then, building niche Web sites and small-scale online stores has become cheap and easy. Free software, advertising systems like Google’s, and “drop shipping” services that allow Web site owners to handle products through a third-party supplier, have lowered the cost of doing business.

Instead of selling goods and services, analysts said most flippers are looking into the easiest way to make a quick buck, by tapping into specialized advertising.

Philip Kaplan, who captured attention with a Web site that rejoiced in the unraveling of the dot-com bubble, now helps sites secure online advertising through his company AdBrite. He said in an interview that he has been encouraging site owners to “carve out a focused niche.”

“All of our advertisers are saying, ‘We want this niche or that niche,’  ” he said. “They never say, ‘We want to advertise on a site about nothing.’ ”

Mr. Hermansen, of bird-cage.com, says he is always looking for areas on the Internet with high search volume and little competition.

“Once I found the bird niche, I knew it was where I wanted to be,” he said.

Before bird cages, Mr. Hermansen owned — and sold — niche Web sites about paintball, remote-control toys and electric scooters. In 2005, he quit his job as a draftsman to flip Web sites full time.

“It used to be that if you had a site worth a million dollars, you’d hire an investment bank or a broker to sell it,” Mr. Mickiewicz, of SitePoint, said. “But if you had one that generated less than that, you’d just have to sit on it. Now you can sell anything for any sort of profit, whether it’s $20 or $220,000.”

The average selling price of Web sites on eBay was $78 last month. There, sites for sale range from online stores specializing in gift baskets and patio grills to message boards and forums devoted to the online game World of Warcraft and deep sea fishing. The marketplace at SitePoint offers sites about chicken recipes, bonsai trees and hiking stories. “Low-maintenance content sites” like blogs, online communities and directories are the most popular, Mr. Mickiewicz said, adding that a Web site’s selling price is generally one to three times the value of its annual revenue.

Peter T. Davis, who calls himself a “Web property developer,” said he owns about 20 Web sites, including message boards about model railroads and coin collecting.

Mr. Davis said he generally holds onto Web sites for at least a few months before flipping them. Sometimes, though, the process is much quicker — like the time he bought a forum about day care centers for $1,500 and sold it six hours later for $3,500.

“I used to make my own Web sites and sell them, but then I realized, ‘Hey, this is much easier than making them,’ ” he said. “It’s as simple as buying a Web site from someone and making it more attractive. It’s about creating value where there was none.”

Creating the value, though, is the tricky part. Many Web site flippers said they begin by tweaking a site’s template and making other superficial changes like adjusting fonts, colors and type sizes. After that, they manipulate a Web site’s structure, coding and presentation so it shows up more prominently in Web searches.

In an era when Web use is increasingly search-driven, making sure people find your site makes all the difference, Mr. Hermansen said. “Once you beef up traffic, everything else just happens,” he added.

Consumer protection groups warn potential buyers. Traffic generators and click fraud can easily exaggerate Web site traffic. Web site owners can inflate revenue statistics and tamper with search engine rankings.

“It’s an increasing law enforcement challenge,” said Lois C. Greisman, associate director for marketing practices at the Federal Trade Commission. “It’s hard to measure fraud on the Internet, but this is just a variation on the classic get-rich-quick scheme.”

Last year, Mr. Hermansen said he did something he had wanted to do for years: he bought a parrot, Sunny. Earlier this month, Mr. Hermansen and his brother, Mike, set up a warehouse and started manufacturing and selling their own line of bird cages.

Now Sunny lives in one of the cages in the Hermansens’ warehouse and is the mascot for their newest Web site, InnovativeCages.com. Mr. Hermansen said he has found yet another Internet void to fill: “the high-end, high-priced luxury cage niche.”

“Of course,” he added, “the eventual goal is to sell the site for a good chunk of money.”