You really should look at the homelessness crisis in more detail, because it cannot be on private citizens to shoulder that burden. There simply isn't enough for individuals, even if they all miraculously organized together in this effort, to fix the issue.

It's systemic, and we need top-down action. Housing people affordably is a scale issue, and larger institutions should be the ones to gather the equity and resources at a scale that individuals simply cannot, especially in the middle of a housing crisis.

For examples of public housing that works quite well, I'd suggest you read into Greek's post World War 2 Social Housing programs, and Singapore's state controlled housing programs.