My understanding is that the German health care system still has disincentives for sporadic work, because you pay a higher rate under the philosophy that "you have to insure yourself first, and make up for the expected lulls in income" or something like that. I read stories on reddit about immigrants getting burned by that when they were self employed.
The biggest disincentive is the progressive tax-rate.
But you stay on your public health-care plan as long as you don't reach a threshold of time spent per week. But of course, if you're an immigrant and never were covered by public healthcare then yes, you'll get burned.
