I copied this from a CSI show. The detective asks "You were living in a house with six people" ( I thought maybe it is "a house of six") But the caption shows "with" on the screen. I knew there were 6 people living in the house. I had asked the wrong question (ambiguity) by copying "You were" in my post. I just wanted to check my own understanding,
If you don't want the sentence to be ambiguous, you need to say "John was living in a house with five other people." Then it's clear that the total, including John, was six.
(By the way -- you can't always trust the captions on tv -- they're not always accurate.)