I have turned two of my hobbies into businesses that are now full-time work for myself and part time work for two others (my wife and an employee we hired a couple of months back).

For me, the fact that you have to sell/market something isn't what makes it a stressful; I enjoy that aspect of it too.

Instead, I find most of the stress coming from the high stakes (if I make mistakes or work slowly, my business will fail and my children will grow up without a present father) and need to hyper-optimise (every single action is about maximising the amount of dollars earned per hour spent working).

I've found immense peace in the last few months in cleaning, of all things. It's not a traditional hobby, but the fact that I can make mistakes (or just not do it at all if I'm tired) with minimal consequences makes it so much less stressful than my businesses which do revolve around "traditional" hobbies.