Summer is quickly sneaking up, and people with dreams of vacationing with the rich and famous and all sorts of VIPS are snatching up properties on swanky Nantucket.

 Sales of single-family homes have more than doubled on the island in the first four months of the year, compared to a year earlier. There were 39 single-family home sales transactions recorded from January through April, up from 17 a year ago.

But sales have declined significantly since the market peak in 2005, when 62 single-family homes sold in the first four months of the year, according to data from The Warren Group.

Prices have also eased a bit, according to local real estate brokers, although you wouldn’t know it from some recent transactions. Just last month, a compound on Hinckley Lane in the Cliff area traded for $5.75 million. Another home, a five-bedroom Colonial with three-bedroom guest cottage at Medouie Creek Road, actually was foreclosed on by JP Morgan Chase. The bank took it back at auction for more than $5.7 million. The property had been purchased in 2002 for $3.2 million, and was listed for sale four years ago for almost $7.5 million.

Brokers like to say that the island’s residential real estate market is driven by discretionary sales and second-home purchases – meaning that owners of vacation homes don’t have to sell because they don’t need to move off the island for a job or lifestyle change and buyers generally don’t have to buy. The market is somewhat insulated from the housing market on the mainland.

But the recent economic downturn affected even the affluent, seeming untouchable, homeowners. It made selling a necessity for some homeowners who lost well-paying jobs, and buying became a luxury that many could no longer afford.