It doesn’t have to be a durable good, it can be a service.
I live in NYC. A monthly unlimited subway pass is 120 dollars. If you can’t afford that lump sum all at one, you can 2.75 pay per trip. If you use the subway 2 times a day (to and from work) for 30 days, that’s 165 dollars... more than the upfront of an unlimited pass.
They lend you $120, and ask for slightly less than $165 back - let's say $145. So you save up the money you normally would have spent on tickets daily and at the end of the month, you pay back the $145, and you have saved yourself $20, while the lender made a return on investment of about 20% (a very respectable amount, given it's unsecured).
For taking on the risk of an unsecured lender, they get a very high interest rate - ~20% a month! That's almost illegal!
That’s why merchant credit card fees are painful for small shops. Ie 3% + 35 cents isn’t so much until your average ticket size is $5 and all of the sudden 10% of your revenue is going to intermediary.
There’s fixed cost associated with moving cash around so that 20% return is likely negative under current infrastructure.
What you do get though is freedom from thinking about the cost of rides, which is pretty great.