Q: My wife and I have rented an apartment in a three-family house in Queens, N.Y., for the past decade. Whenever our son is on rotation in the U.S. military, we dog sit his golden retriever. Our original lease gave us permission to do this, but it expired years ago and we’ve been on a month-to-month agreement ever since. We are now dog sitting again. The other day, the landlord told me that the building allowed dogs only under 20 pounds, even though our original lease did not include weight restrictions. (Other tenants in the building have dogs, though theirs are smaller than ours.) The landlord then told me that we could move out at any time. Can he really evict us?

A: Your position is precarious because you are living on a month-to-month rental agreement. Your landlord could decide to end it at any time — with proper notice — as long as his actions are not discriminatory. In your case, he could terminate the lease with 90 days of notice, under New York law. So, if he decides he’s had enough of bigger dogs in the building, even if the original lease allows pet-sitting, you could lose the apartment, according to Darryl M. Vernon, a real estate lawyer who represents people with companion animals.

But hope is not lost. Your landlord does allow dogs under certain circumstances. “They may be able to work this out,” Mr. Vernon said.