This is a problem specific to Jerusalem where properties were built on land leased from the Greek Orthodox Church where the original leases were for very long periods of time. Many of these leases are now coming to the end of their term and there is a great deal of uncertainty as to what will happen – will the leases be renewed? Or will the lease expire and the property have to be returned? You could potentially end up having to relinquish your home for no money when the lease is up, so it's potentially a very serious problem indeed.
Your lawyer should be able tell you if the property that you are looking at is on Church Land or not. Expect the value of these properties to be significantly lower than those built on private land.