There are a number of mansions in Binghamton, but I have a feeling that this was actually some sort of boarding house rather than an actual mansion. I found an article in the November 3, 1900 issue of the New York Times announcing the death of a salesman, John Higgins of Binghamton, at the Mansion House. Higgins, a traveling salesman for the Beck Cigar Company, was despondent over family and health problems. He committed suicide by eating two ounces of rat poison. Higgins left behind a wife and four children.
Here's the back of the card and the message, which reads:
Wishing you a happy Easter
I am your brudder