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How does a bank make money on an interest free secured loan?
The bank depends on the laws of large numbers.  They don't need to make money on every customer -- just on average. There are several ways that zero interest makes sense to them: You asked about banks, and I don't think you see this last scheme in use very much by a bank.  Here's why.   First, customers absolutely hate it - and when you drop the interest bomb, they will warn their friends away, blow you up on social media, call the TV news consumer protectors, and never, ever, ever do business with you again.  Which defeats your efforts in customer acquisition.  Second, it only works on that narrow range of people who default just a little bit, i.e. who have an auto-pay malfunction.  If someone really defaults, not only will they not pay the punishment interest, they won't pay the principal either!  This only makes sense for secured loans like furniture or cars, where you can repo that stuff - with unsecured loans, you don't really have any power to force them to pay, short of burning their credit.  You can sue them, but you can't get blood from a stone.