If you plan something like this, make sure you check with your employer first. I know that a lot of contracts do have clauses which require an approval from your employer before starting another side-business
San_Francisco already answered that correctly. I have a B-permit, and I already registered two GmbHs in Switzerland. It’s absolutely no problem. You might want to check websites like startups.ch for more information.
You don’t even need to start a GmbH for your stuff. Individual company will make much more sense in your case. For GmbH, you need 20k cash at the start.
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