They could absolutely spend it all / get an addiction etc. The beauty of a UBI though is that next month they get it again and can start over. There is always the ability to start again, every month is a renewal. These setbacks that currently force people into the streets and doom them for a lifetime would now have the potential to only be setbacks. Of course there will still be homeless people and addicts, but at least every month they will have money for food magically appear in their bank accounts.

The current system results in widespread homelessness, despair and inequality. To say we are going to stick with what we have instead of giving everyone the basics to live a decent life makes no sense. We are sticking with a known flawed system that punishes the poor because a few people may not play by the rules in the new one.

Why would charity drop off, if someone is charitable, now they have more to donate. People are also easier to help because they are starting from a solid base instead of nothing.

As far as being at the mercy of the rich, we are already there. If everyone had an income, they could actually band together if they wanted and use it on projects causes that are important to them instead of just the constant struggle to survive.