Krolow owns several islands in places like Canada and the Caribbean. He said the rentals of those properties act as a key revenue stream, forming around 25% of his annual income — the rest comes from commission he makes off of island sales.

You can only use the island for a specific time - meaning that the longer you own the island, the less the developments, for which you have paid, are worth. If the lease is for a specific use and you wish to change the use, you may lose your rights to the island.

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.