Good food, exercise, water, and proper sleep will take care of most things.
But every once in a while someone breaks a finger. (Or gets an infection that won't go away, sorry berberine)
I've been contemplating this question, and (as a US citizen who does NOT have health insurance - currently illegal) have had to visit the doctor a couple times in the two years since my care was dropped. In the US there are many urgent care clinics popping up. I can usually see a doctor for $100-$150, and medications (like steriods for a serious case of poison ivy) cost between $4-$27. I make about half the federal poverty line. I do not use entitlements, and make sure I have an emergency fund to cover events like these.
However, creating a basic safety net would
be nice. I recently took a regenerative livelihood
course through Gaia "U", and one of their more interesting systems was "Income Solidarity." It established a baseline income, and, depending on your monthly income above or below the line, at a percentage of your choosing (you can choose to be "IN" for a lot (10%+) or just try it out (1%)) you either contribute to the general fund or draw from it. Eventually over a decade they had a running surplus, which members could drawn out an interest-free loan in the event of major crisis or opportunity.
This could be a great system for community supported health care. There are many variables - trust between members being a huge one - and it would take time to establish. There is big potential here.