Seoul has fewer people living on the streets than Los Angeles. But tens of thousands live in illegal units so small there is barely enough space to lie down.
A little bit off topic, but still related. Yeah, Soul is kind of rediciolous, half of the 40 milion population of Korea cramp into one city 20km from the North Korean border. The housing is so expensive here that people don't marry and don't start families because they can't afford it. But still all the work is only here in Seoul so either you live in a super expensive flat or you commute for 4 hours a day (which some people do).