Some islands can be bought undeveloped, while others already have roads and/or houses. Islands are also available for rent. Many celebrities have their own private islands. Commercial development of uninhabited islands can raise ecological concerns, as many have a fragile environment.

More than two years passed before he could get another commission but by then Krolow had 80 islands for sale, in different parts of the world. He also started buying islands himself. He and his company now own more than a dozen islands — in Canada, Panama, Belize and Fiji — which are rented out as holiday lets.

You can find private islands for sale via Private Islands Inc. or Vladi Private Islands, or by contacting a realtor who specializes in big-ticket sales. Additionally, some high-end real estate companies, like Sotheby's International Realty or Christie's International Real Estate, list private islands for sale.

Can you buy a private island? Yes. In most cases, you will need a deposit of 10 percent of the purchase price to enter into an agreement of sale. You will also need to arrange for a jumbo mortgage or private financing to cover the remainder of the purchase amount.