In Germany it's common consensus that payment is done once the work is finished and billed accordingly. Of course for prolonged projects you agree on several installments.
Just recently I learned that according to law your monthly utility payments (for flats) are still your money until you get a proper bill.
In the US, I think it's more common to charge after. I worked at an agency whose paperwork stated they would charge before the session, but they never actually did.
Personally, I'm not gonna cancel a session just because the card declines anyway- I can be paid another time; so it's much less awkward to just charge after imo
US checking in, of the 5 or 6 therapists I've had and the similar number my ex spouse has had, I think only one charged before a session. There's a couple I'm not sure on because it was covered entirely by insurance and we were never directly billed so can't say the timing
In Denmark you pay after the session - I've been one place where it's monthly invoicing, and another where it was payment after each session (by credit card I think)
In the NL there is only private health insurance, so it's technically private sector. I pay my 120 EUR premium, and this was included so I never needed to pay at the time of care.