I had a silent neighbor, as well, back when I lived with my parents. He was probably 50+ years old. For a long while, he apparently lived there in order to take care of his elderly mother. She passed at some point and it was just him.

He was silent in a bit of a different way. We would see him leave in his car sometimes, but half of the house was glass windows and we would never see him in the windowed portion of the house. Lights were never on in those rooms, either.