I disagree with your first statement. People absolutely can and do provide many things of value while the mental health is declining. In fact, being able to provide things of value is often what helps with the mental health. Don't take that away.

Seeking shelter to heal is certainly one good option, but I also encourage everyone who struggles to seek out help. That's not a fight you have to fight alone. If out break your bone, you see a specialist for fractures. If your mental health is damaged, see a specialist for mental health.