It really will depend on the country

If you're using a credit card, you specify at POS how you want to split the purchase (Number of installments, or cuotas in spanish), if it's free of interest will depend on your deal with the bank (And if the seller has different plans)

It's common for even the worse cards to charge interest at least from the third month onwards, but most banks have special deals with seller of costlier products (I'm pretty sure I could make a car payment with 0 interest (to my card))

Can't comment further, but the US has always seemed particularly backwards regarding their banking: - Needing a third party to allow instant transfers - Mobile POS being weird / Needing to take a card away from a table to charge it - How common checks are - Overdraft fees