HONOLULU -- For $6,500 a night, 18 guests can lounge in a 10-bedroom, beachfront mansion on Maui's south coast. On Oahu, a spacious four-bedroom home on the affluent Kahala neighborhood is listed for $2,500 a night and welcomes up to eight people.

Thousands of private vacation deals have been springing up across Hawaii as visitors look for alternatives to crowded hotels. Isle residents, in turn, are cashing in on their properties, advertising online packages that now offer French chefs, maids and even spa services.

Despite land-use ordinances restricting such rentals to residents who obtained permits before the late 1980s, short-term private rentals are growing beyond control. Residents say they bring traffic and noise into tranquil communities and make it harder for people to find long-term, affordable rentals and leases.

"There's no sense of community, because you've got strangers coming in all the time for two to three days," said Kalana Best, who lives in Kailua and joined the Save Oahu's Neighborhoods, a nonprofit working to preserve residential areas. "It's like a tsunami in slow motion, but instead of a wave of water, it's a wave of people."

As concern grows, the state Tax Department is investigating 216 rentals and bed-and-breakfast operations in the islands that may violate tax laws.

On Oahu, only 1,000 homeowners have a certificate that allows them to rent rooms for less than 30 days. However, there are more than 2,000 online advertisements for the rentals on the island, according to a 2005 state study.

Legal vacation rentals on Oahu are limited to homeowners who applied for a certificate to operate before a ban on short-term residential rentals in the late 1980s. New applications are no longer accepted. Other counties either don't have a permitting process or have limited enforcement, said Marsha Wienert, state tourism liaison.

The trend could be driven by regular island visitors who are exploring other options to Waikiki, said state tourism liaison Marsha Wienert. Hotels were especially busy last year when Hawaii welcomed a record 7.4 million tourists.

"Visitors -- especially as they repeat -- are seeking different types of accommodations," Wienert said. "And because it has become such a lucrative market, people are not going through the process and getting the type of zonings that are needed."

On Kauai, luxurious home rentals make up about 40 percent of all housing in the rural town of Hanalei, according to F. Kenneth Stokes, an economist with the Kauaian Institute.

Residents on Oahu and elsewhere are lobbying for tougher enforcement against illegal vacation operators on all islands.