OK, hate to be a spoilsport, but you should consult with an attorney/legal adviser about language in your lease agreement, also. What if someone transplants in a pest that hitchhiked on a plant, or worse, some noxious, spreading weed because it had a "pretty flower"? Who will be held liable and responsible to clean out the mess/get rid of the pest? I don't know what part of GB you're from, but you may want to check on things weekly? until you're comfortable with the renter's gardening skill level. Or perhaps have a good neighbour check up on them? I'd start with gardening friends as lessees first (treat them as any other renter--get everything spelled out in writing). I know I'm pretty pessimistic for a gardener--my day job influences me, sorry. Keep us posted as to how it goes, you've piqued my interest.