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.
First, let's get our terms straight so we're on the same page. You can think of gears as the same thing as speeds -- a bike with 18 gears is an 18-speed bike. Bikes generally have 1, 3, 18, 21, 24, or 27 speeds. (10- and 15-speeds are obsolete and you don't see them on new bikes any more.) Lower numbers are the low gears, and higher numbers are the high gears.