All you have to do is ask yourself, if you were getting this basic sum, would you be content to do nothing? The answer is probably no. I would do something, some kind of job, as would many people. If only for their sense of self worth / self esteem. I believe that almost everyone would get a job even though a basic income means they don't have to. Also keep in mind, that no matter what you do, there will ALWAYS be people who refuse to work. You could make unemployment punishable by death, you still wouldn't be able to force those people who don't want to work to do something. That's just the way it is. So the only thing you can really do is pay them to stay out of the way and not cause any problems. This is cheaper than buying a gun and being eternally vigilant, or paying for security measures.

Severe disincentives to crime aren't as useful as you think, because those committing the crimes do so because they don't think they will be caught. Look at some of the absolutely medieval penalties they have in the middle east for various crimes, and yet they still have criminals.