What taxes do the homeless pay? They are receiving far more in benefits (think food stamps, free health insurance, free public transit, etc.) than they will ever pay in sales tax. I agree that housing is the solution to the problem, but let's not weaken our arguments with laughable claims. 
And let's not lose sight of the fact that allowing them to takeover public areas for their own personal use at the expense of others (been to a public library lately?) only diminishes any sympathy for them. 
Let's treat them as they are, people in need, but not with special rights.