In the past year, hotel chains and home-sharing sites have started encroaching on each other’s turf. Airbnb Inc.advertises hotel rooms on its platform and Marriott International Inc. recently launched a home-stay offering.

The latest player to blur the lines is short-term rental start up Sonder. The San Francisco-based hospitality company is expanding beyond its network of custom-designed vacation apartments, signing leases with 17 off-the-beaten-path, mom-and-pop style hotels in New York, London, Dublin and other cities in recent months – and is negotiating an additional 40 properties.