Buy two for the price of one: It's an offer commonly used by pizzerias, grocery stores and taverns to increase sales.

Dan Pool and his wife, Kelly, are dangling a two-for-one deal on the biggest of big-ticket items: homes.

The concept is proving wildly successful.

The two own and operate Two 4 One Real Estate, a franchise company that has five offices in Tucson and has plans to expand nationally.

"Our business model is based on a buy-one-get-one-free real estate commission," Pool said. "We actually sell a client's present home for free and in exchange the client agrees to buy their next home through us. This allows our sellers to keep more of their equity in their present home, while allowing us to earn a commission from the seller or builder on the next home they purchase."

Since adopting the strategy five years ago, the Pools' income has increased 38 percent to 45 percent annually. Last year, the couple made $344,000, waiving $100,000 in real estate commissions in the process.

The Pools, who formerly worked at RE/MAX Premier Realty, started their own company, Power Plus Realty, five years ago. They stumbled on the two-for-one formula when a pilot stationed at Davis-Monthan Air Force Base asked them to sell his home.

"He had very little equity in his house and had just enough to pay a buyer's agent commission, but there was no way he could come up with $3,500 for the listing fee. But he'd already been approved to buy a house, so my wife and I decided to waive the listing commission. We figured it would be better to get a piece of pie, rather than no pie at all."

Pool, 43, told the man he'd waive the listing commission if he bought his next house through Power Plus Realty, a Southeast Side agency now known as Two 4 One Power Plus Realty.

"We made $5,000 on the next house he purchased. He was happy because he moved up to a bigger, nicer home, without paying any commissions; and we were happy because we had a guaranteed sale and a devoted client."

The pilot spread the word about the deal he received and soon others, even those who could afford to pay all fees and commissions, were calling the Pools to seek similar treatment.

Tom Wedic, 42, heard about the two-for-one concept in a direct-mail flier.

"Not only did I save $5,000 on commissions, but Dan negotiated the price of our new home down by about $15,000," he said.

Asked if he would use Two 4 One again, Wedic replied: "I wouldn't go anywhere else."

Randy and Sistine Castellini bought a Two 4 One franchise in March 2004. They own and operate Two 4 One Umbrella Realty on the Northeast Side.

"Last year, we grossed about $120,000 and we're on track to double that this year," said Sistine Castellini, 36. "There are several things we like about this business. It creates a tremendous referral network, our clients are happy and we're dealing with extremely motivated buyers."