Homelessness in America is mostly a drug and mental health issue than it is an affordability issue.
This is exactly backwards https://www.skeptic.com/reading_room/critical-analysis-of-americas-homeless-crisis/
Counterfactual reasoning can be a useful tool for determining causality. You think A causes B. Remove A. If B still happens, then A was not the cause. (The rooster crows and the sun rises, in David Humes famous example, but no one thinks the rooster causes the sun to rise, which is easily testable by silencing the rooster and noting that the sun still rises.) Employing counterfactual reasoning here, if drug use were a driver of homelessness in aggregate, we would expect states with higher rates of drug abuse to also have higher rates of homelessness. In fact, no such relation exists between the data on drug addiction and those on homelessness: West Virginia, which leads the nation in drug overdose deaths,7 has one of the lowest rates of homelessness in the country.8 Californias overdose death rate is about one-quarter of West Virginias!9 Nor can state-level variation in rates of mental illness explain variation in rates of homelessness. Mental illness can be difficult to quantify, but Mental Illness America estimates that Californias rate of adult mental illness is about the same as the national average. ... As in the above summary of differing hypotheses, Colburn and Page Aldern tested different explanations for homelessness by looking at regional variations in homelessness rates. However, they analyzed more finely-grained data, relying on city-by-city comparisons instead of state-by-state ones. After investigating a number of non-housing explanations for large-scale homelessness including climate, generous welfare benefits, mental illness, and substance use disorder they concluded there was no evidence that these factors can explain why some U.S. cities have significantly higher rates of homelessness than others. Instead, they write: Vulnerable households live in every city of the country; the differences in rates of homelessness can be attributed to structural factors associated with the housing market. Homelessness is most severe in the metropolitan areas where housing costs are highest, because the pricier that housing becomes, the greater the risk that people with low incomes or other serious challenges will be locked out of whatever homes are available. This is not a new finding. In fact, it is the consensus among most serious researchers of this problem. In their definitive book on homelessness, In the Midst of Plenty, Marybeth Shinn and Jill Khadduri note that homelessness is essentially a lack of access to affordable housing. Similarly, an influential 2018 study by Zillow (a leading online housing information and analysis site) found that rates of homelessness increase fastest in cities where, on average, rents exceed one-third of income. It follows, then, that the cities with the most severe homelessness problems also have sky-high rents. The most recent Consumer Affairs ranking of U.S. cities by housing costs looks a lot like a list of places bearing the brunt of mass homelessness: San Jose, San Francisco, San Diego, Los Angeles, Seattle, New York, and Portland all make it into the top ten.