Landlord and tenant should negotiate whether they will request waiver of subrogation clauses in their property insurance policies, liability insurance policies, or both (it is less common for the parties to request waiver of subrogation clauses in liability insurance policies, but possible).
Since Nick's answer covered average speed over the entire lifetime of the bike, I'll cover the average over time spent moving. Simply put, this depends almost entirely on the cyclist, rather than the bicycle itself, and there is a wide range. Casual recreational cyclists probably average around 10-15 km/hr (6-9mph). This is your weekend trail rider, out to enjoy the view in the local park.
For road bikes, 18-22mph is pretty average. The world speed record is about 82mph unassisted but that is with a special aerodynamic recumbent bike and athletic rider on the flat desert highway. It is a lot faster with drafting a car or train. In a velodrome or on an exercise bike it can also be faster.