Must be mostly honest here in the land of convict heritage.
Boat sat on marina for 10 years before we got her, no ignition keys and doors unlocked.
Never even saw a broker when we bought her,,just told where she was and to climb aboard and check her out.
We at one stage experienced a fuel theft problem I fitted a ball valve directly under the deck fuel filler. It serves two purposes stops access to tank plus limits any ingress of water through the filler cap should the seal fail