There is no way to make someone pay what they don’t have, and poverty level means that is what it takes for a single human to survive. There is nothing left of it to tax, take 10% and you either give it back in welfare or they die.
It would also encourage everyone to work at least enough to make that tax free 12K. They might learn to become productive and get a real job.
What was that Scrooge said about the surplus population? But seriously, most of them will straighten out enough to survive, and few will "die" as we are a charitable people.