This comes up regularly. Some hosts see no issues, but many recommend NOT renting or loaning such items for two reasons: 1) AirBnB's liability policy won't cover this once the guests are off your premises, and 2) it's highly likely that your own insurance won't either.
We used to have a loaner bike, but we've discontinued that. Instead, we provide printed information for multiple bike-rental options near our place. We can also point guests to canoe/kayak rentals.
If you decide to pursue equipment rentals for off-site use, I suggest contacting your home-insuror for liability options they might offer.
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