Resort-home owners are often wealthy Mainlanders in their late 40s to 60s whose tax payments and consumer spending provide a significant boost to the state's economy.

Real-estate consultant Ricky Cassiday, who compiles data on Hawai'i's resort-home market, says he expects sales to continue to climb in the years ahead as more well-to-do baby boomers retire and look for desirable locations for their second homes.

Maui is the state's fastest growing location for resort homes, and Maui Mayor Alan Arakawa says he is concerned about the impact of the building boom on a number of fronts.

For starters, the increased demand boosts prices and "takes them well out of the range of the local community," Arakawa says. "It forces the local community into a noncompetitive state and it's a tremendous area of concern."

What it means for tourism is "the whole industry is shifting and evolving," Arakawa said. "It's very important for us to understand that there is an inherent conflict between the development industry and the tourism industry and our need to be able to protect the tourism industry."

"We have large homes being built on our mountain slopes or large areas are being developed where sugar cane was once the predominant scenery," he said. But "people don't come here to see houses on hillsides."

"People who come here to see forests don't like to see roadways going to houses," Arakawa said. "When you're out on a catamaran you don't want to look up and see houses. All these things are being affected in an adverse way by the construction."

Mainlanders are also a driving force in the Kona real-estate market, said Larry Hull, a broker at Clark Realty Corp.

"That's where the majority of our buyers are coming from, especially California. It's a very hot market," he said.

The average sale price for a single-family home in Kona has risen to $663,000 from $450,000 a year ago, Hull said.

For kama'aina homeowners, the rise in prices has improved their equity positions, he added. "The people who own property definitely like it. They certainly achieve some appreciation."

Hawai'i Tourism Authority executive director Rex Johnson said growth of the vacation-home industry is an issue that needs to be addressed because it takes up prime land and resources. He said the tourism authority plans to commission a study on the issue.

Marsha Wienert, Gov. Linda Lingle's tourism liaison, said the issue has drawn more attention over the past couple of years, with particular concern expressed over the impact on neighborhoods and communities.

But she adds that the vacation-home market is becoming an integral part of the overall tourism industry.

"My guess is it's fairly large and it's increasing," Wienert said. "It's been large on the Neighbor Islands but it's getting big here on O'ahu."

Ocean Villas at Turtle Bay Resort is one of the new developments on O'ahu. The oceanfront condominiums range in price from $1.5 million to $2.5 million, and the 57-unit project was more than half sold within two weeks.

"They like the North Shore because the North Shore is not as crowded," said Joyce Timpson, a spokeswoman for Ocean Villas. "They like the ambience of old Hawai'i."

At Kapolei West, a proposed golf-course community with about 2,400 homes adjacent to Ko Olina Resort & Marina on O'ahu, developer Campbell Estate expects nearly 1,000 homes, or roughly 40 percent of the project, will be sold to second-home buyers.

Wienert said vacation homes offer a variety of accommodations that today's travelers are looking for.

"You get folks here as visitors for the first time. They fall in love with it and they come back and it's nice to think they want to invest here," Wienert said. "We've seen a huge investment because of that whole baby boom generation and their wealth," as well as the volatile stock market that drove investment to real estate.

"They're really looking at where do I want to be when I retire, or as I start cutting back on my workload, where do I want to spend my winter months?" Wienert said. "This is where they want to be. Years ago they bought a condo. They're a lot more wealthy today, so they're buying and building homes."

They are attracted by real-estate prices in Hawai'i that are lower than prices for comparable land and properties in areas like northern California and New York. And unlike some other places on the Mainland, Hawai'i still has oceanfront property available.

Many planned resorts are designed to cater to second-home owners with features such as golf courses. The hotels in resorts provide restaurants and guest lodging for vacation home owners, too, said Ann Mapes, president of Belt Collins Hawaii, which has helped design projects including Four Seasons Hualalai, Mauna Lani and Mauna Kea. Hotels can also attract potential home buyers.

While vacation home owners don't pay hotel room taxes, they more than make up for it with the hefty property taxes levied on their pricey properties, real-estate consultant Cassiday says.

"And there aren't a lot of these people who are sending their kids to (public) schools," he says. "This is like money falling from heaven (for local governments)."

Nonetheless, Hawai'i also needs to plan for growth in the vacation home market because of its potential impact on the real-estate market, land use, water use and roadways, Mapes said.