What is it and when to act?
When you go self-employed, your employer-based insurance ends. The question must be resolved immediately — before any gap in coverage arises. Notify your insurer at the same time you register with the Finanzamt.
Three main options
Voluntary GKV — stay with the same insurer, pay yourself (minimum ~€215–260/month).
PKV (private health insurance) — cheaper when young, more expensive with illness and age. Returning to the GKV is difficult.
KSK — for artists, designers, journalists, musicians. The government pays 50% of your contributions. The application process takes several months.
I stayed with the GKV voluntarily — minimum contribution €250/month. Tough at the start but no nasty surprises. I didn't go to the PKV: I know people who are stuck there and can't get back into the GKV.
As a designer I applied to the KSK — the process took 4 months and I had to prove the creative nature of my work (portfolio, contracts). In the end I pay half what I would pay in voluntary GKV. The effort is worth it.