"In" is correct here. Here are a few "in" versus "on" examples: "We live in this city", "We live on a farm", "We live on potatoes", and "We live in poverty" As a native English speaker, I'm not sure of the exact rules, but I think "on" is used when there is a dependence (a person depends upon potatoes) and "in" is used when the subject is "part of" something bigger (a person is part of a city).