I got some info back from my friend who is an insurance broker. Here's a summary of what he told me:
One residential insurer in Canada (CNS) will cover 2 boarders living in a home, provided that the owner also lives there. However the boarder(s) must be a long term one (i.e. over 30 days) so in the case of Airbnb rentals, this likely means that guests wouldn't count as boarders.
It seems the only way to cover off this operation is to get a commercial policy, and the occupancy/operations would be deemed a rooming house. For a standard home valued at $300,000 (replacement cost), the annual cost would be roughly $1,700+ for the building and $750 for a $1,000,000 liability policy (total $2,450). Mainstream insurers view rooming houses as a substandard risk so you'd have to get a policy through a specialty company such as CanSure or Beacon. However, your insurance broker should know which specialty markets will write these risks.
If anyone needs more info or would like the contact for my friend to get a quote, please let me know. I hope this is useful for everyone! Let me know if you have any more questions and I'll do my best to find out.
**Please not that this is only relevant within Canada and these are just rough estimates, not actual quotes. I'm not a licensed insurance broker and this is not a guarantee or offer of insurance.