Land ownership is highly recommended.
If leasing you need a (long term) leasing agreement signed by the landowner giving adequate notice when they plan to sell the property, for you to find a new home (if needed). Furthermore, that they agree that you can operate a sanctuary, rescue, or microsanctuary on their property.
If the land on which the farm sanctuary operates is owned by the founder(s), a highly recommended best practice recommendation for the safety of the non-human animals, is to have a long term leasing agreement between the farm sanctuary founder(s) and the farm sanctuary.
Some farm sanctuaries, after many years of becoming more established, were able to buy the land from the founder(s) at a later date. Some founder(s) or other landowner(s) have it as part of their retirement plan to leave the property to the farm sanctuary. This should not be left to hand shake agreement, but a legally signed agreements.
Again, this is all to make sure the non-human animals in the farm sanctuary’s protection are protected, because the things can and will always happen or change.