There's a show on TV about this called "How Clean is Your House?" or something like that. The people featured are generally young professionals. They're not mentally ill, just lazy pigs.
It's worth checking out. My favorite episode involved two 20-something Asian sisters whose bathroom was so caked in mildew that the team of inspectors had to don hazmat suits before entering it. The bathroom had to be gutted.
Surprisingly, the sisters were able to keep the house clean. They passed inspection months later.
"No one ever showed us how to do this," they said.
I was watching one with a girl who was a working professional. Her apartment was so filthy. More than that, she had MONEY all over her floor and bathroom,etc. Those two old ladies must have collected hundreds of dollars by the end of the show.