I do agree that there are plenty of people who will not use any money given to them in any productive way, but is it possible to regulate this way? You could have some sort of program where homeless and jobless can apply for a job with no chance of rejection; only a wait-list if there weren't currently enough jobs. You could only apply once though, and if you didn't behave well and work hard, you'd be kicked out of the program permanently. During this period any rehabilitation necessary would be given free. After the 6 months, if successful, you would be given options on how and when to pay back what you have costed the government. You'd probably also be granted some kind of certificate testifying your aptitude for work.
Those who drop out of the program would receive less payment from the government than before, if any at all.