the party that is screening and contracting with the tenants. A short term rental endorsement will cover him for short term leases he is contracted on but will do nothing for a contract signed between his tenant and a third party. Running a business on the premises of a landlord policy is a specific exclusion on nearly all fire/dwelling policy forms. This falls into the same category of on site businesses like dog sitting, day care, ect.

Airbnb does offer a $1,000,000 guarantee. It is not insurance by the way and is up to their determination if a case meets their criteria. It is not bound by state insurance laws.

There may be a solution but he would want to ask his insurance company how to go about it.