Not as rare as you might think. The separation of land and buildings and the leasing of land to the owner of the buildings is an old, established and widely-used mechanism. Many substantial commercial buildings are on leased land, perhaps the most famous of these being Rockefeller Center in New York City. There are large areas where people own homes of leased land: Baltimore Maryland, Davis County California and many other regions. It is now becoming more common for developers to establish residential projects on leased land.
Outside of the United States, it is not at all unusual. Since World War II, for instance, nearly two dozen “new towns” have been established in Great Britain- most of them on leased land. In Israel, most rural settlements are built on land leased from the Jewish National Fund.