Living on the edge means living a dangerous and/or unusual everyday life.
People who live on the edge are very frequently exposed to phisical, psycological, economical, lawful or other kinds of dangers.
Examples for
people who live on the edge:
Extreme-sportsmen, gamblers, policemen, thiefs,
human-rights-activists, rappers, etc.
-My
friend John is living on the edge.
-Oh
yeah? He is a gambler or something?
-No, he cleans
windows of high office buildings.