Doesn't sound like a good business for what you need it for. I think that US (probably Canadian as well) citizens could rent from the guy only if they had their own insurance in place as most insurance companies in the US (again, not sure about Canada)allow the policy to follow the driver, so if you are driving a friend's vehicle, have an accident, and the friend is not insured, at least you are, if the accident is your fault. However, comprehensive and collision insurance is above and beyond the minimum required (liability) and comp and collision is what protects the vehicle you are driving. So even if a US citizen were to rent from this business, had their own liability coverage (I think it's called 3rd party in the UK?) and were to lay the bike down, let's say, to avoid a deer crossing the road, they would still be personally responsible for the damages to the rental bike.
I don't think the owner has thought the business through, unless he plans to carry low-cost bikes and do rental/purchases, which would allow the purchaser to gain title, and hence be able to insure the bike. In the US, insurance is pretty much a given for any business, especially a transportation related one.