A paying lodger is a change in occupancy
A homeowners form is written around the people who live there as a household. Taking rent from someone who is not part of it introduces a commercial element, and carriers treat that differently: some accommodate it with an endorsement, some limit how many lodgers, some decline. Doing it quietly is the version that fails at a claim.
Their belongings are not yours to insure
Your policy covers your personal property. A lodger’s possessions are theirs, and they need their own renters policy. Owners frequently assume a shared roof means shared cover, and it does not.
Liability widens with the arrangement
A paying occupant and their visitors create exposure on your property that an ordinary household does not. Where money changes hands, the liability analysis changes with it, and the limit set for a family is rarely the right one.