I believe the Australian & UK systems work a bit like this, too. Perhaps it's nominally a loan, but collected like income tax, with a threshold on how much you

I believe the Australian & UK systems work a bit like this, too. Perhaps it's nominally a loan, but collected like income tax, with a threshold on how much you must earn to pay at all. However I don't think either is very flexible about different places charging very different fees, or different implied interest rates.