Four incomes is the number of full-time jobs paying typical (most obtainable) wages. Presumably that would be 4 people.
In my market: In mid 1990s one person could afford basic bills on typical, full-time wages. By 2007 living costs had doubled, most due to housing increases. For the next 12 years, wages and living costs mostly kept parity until 2020.
During 2020, basic bills (mostly housing) rose and a typical wage-earning home required ~3 incomes as rents shot up. By late 2021 we were firmly at 4 incomes while everything shot up, especially housing and insurances.
> The median wage earner in the US working one job is not homeless.
Median wage goalpost is up the field from the typical wage goalpost. The latter is the most obtainable income range, the sort that folks could once earn and stay housed.
source: I once supported my young family on a typical wage
Past that, homelessness and wage earning are generally at odds with each other. This is for a for a number of pronounced reasons, obvious and not. One of the less discernible reasons is that being unhoused makes employers uneasy; I once lost a job when my boss learned I was homeless.
In my market: In mid 1990s one person could afford basic bills on typical, full-time wages. By 2007 living costs had doubled, most due to housing increases. For the next 12 years, wages and living costs mostly kept parity until 2020.
During 2020, basic bills (mostly housing) rose and a typical wage-earning home required ~3 incomes as rents shot up. By late 2021 we were firmly at 4 incomes while everything shot up, especially housing and insurances.