I do hope your sister in law is dealing with reputable agents. We've had the same situation around here for the Rowing & ParaOlympic rowing events. I suspect all kinds of people are setting themselves up as agents & creaming off a nice fat comission.
Also your s-i-l should make sure she clears this with her contents insurance provider as if she comes home and finds her property trashed or damaged in any way, she could find that she may not be covered by insurance if the property has been rented out. Actually she might be better off sleeping on her living room floor in a sleeping bag and simply letting our her bedrooms so that she's still there and in control of the situation.
