My last 2 articles in Medium generated $500 and +$800 (and growing) for a total effort of around ~6 writing hours per article, so I think it is a very viable way to make a living writing 100% online.
The point is that if you don't have an audience/publication, no one will find your article. That's why it is usually better to publish your content under a publication focused in the same topic than your article. If you are lucky, Medium will also promote the article in their newsletter and in Medium homepage and visits will boost.
Then Medium pays you a fee based on the article performance. It is not clear what parameters they consider to calculate the fee, but it seems to be a mix between views and reader time.
The last one was published under Medium paywall in June. $824 until today.
What's the requirements to use this medium pay thing?
Do users have to pay to view the article? I don't think this works for me if it prevents HN visitors from reading it.
As a writer, you simply need to sign up for Medium Partner Program (and complete the KYC sending your ID, bank account details, etc.). They pay quite well (the first week of each month).
Medium gets revenues from premium users who pay $5 per month and distributes all the revenues based on views, reading time, etc.