This is basically the difference/choice between giving the kid a break so that he can get to a better place and being his crutch so he doesn't have to.
I think it's totally fair to say "I'm willing to give you this job and even be a reference for you as you try to get other jobs later, but in order to keep this job, get paid, and get a good reference from me, you have to be reliable, show up on time, stay on schedule, and do good work. If you end up back in prison, or don't show up to work for anything other than being legitamately sick, you will be fired. And you won't get a second chance."
But, if you're constantly willing to be there for him when he needs legal advice, work, a place to stay, etc. and you don't require anything from him in return as far as changing his behavior, then as someone already said, you're enabling him. He doesn't have to change, because you will always be there for him to help him pick up the peices and make some extra cash on the side.
It sounds like you might be the only responsible adult he has in his life, so maybe it's time to enact some tough love. Give him some choices, offer rewards and consequences for certain behavior and then stick to it.