If distance isn't important, you can buy an island in the Pacific Ocean, England, Scotland, Greece, Sweden, and other countries. Some island buying tips from Terry Arellano, author of How To Buy A Private Island - A Guide to Ownership. Good soil and vegetation can making living on your island much more enjoyable. Severe climates, hurricanes, tidal waves and abnormally high tides should be investigate before you make your decision. You'll find water is the most important element on an island.
Every island has some variety of options to obtaining fresh water.
Look for a ground water table high enough to dig a well. If a well already exists, have it inspected to insure it's dependable. Fresh water can often be gotten from a cistern and catchment arrangement for collecting rainwater. Check the annual rainfalls. Obviously, you don't want to buy an island near a mainland where guerillas are fighting to take over the country.