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 instance, the typical top end MTB gearing, with a 44t big ring and a 12t rear, and a typical cadence of 90 RPMs gives you a speed of 26 mph possible. The same cadence in the top gear of a compact double road bike, a 50 x 11 usually, gives a possible top speed of 33 mph, at the same level of effort.