Private islands come in all shapes and sizes and can cost anywhere from $200,000 to $200 million, depending on what you're looking for. However, buying an island and building on it is a major investment of both time and money, so it's important to find the right one that's worth waiting for.

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.