Just wanted to chime in:
This idea COULD work, but only if you can offset the risk of missed payments wholly to the service provider (the payment collector), and still stay within the margins. Meaning you get a full payment (minus the service fee) straight away from the service provider, and the service provider takes care of collecting the payments.
For example:
Customer wants to buy a Pandora for a total cost of 500€
Service provider (SP) pays 450€ to OP immediately (if SP deems the customer eligible, that is)
OpenPandora (OP) sends Pandora to either SP or directly to customer (*)
Customer pays a 200€ downpayment to SP
Customer also makes monthly payments of 25€ to SP (for 12 months, so 300€ in total)
(*): after this point, OP will only be involved with warranty, repair and refund issues, and always directly with customer
If at any point the customer misses a payment, it's 100% SP's burden to get it. OP is already out of the picture. It's also crucial that the SP always pays first. This guarantees that even if the SP for some reason goes bust, OP is still on the clear. And I think we can all agree that OP's past endeavors are enough proof that we can't afford to risk any further. And if you can't get the SP to make this kind of deal, then you quite simply shouldn't go forward with this idea.
I know this is kind of a pipe dream, and that OP isn't in a position to make these kind of demands. But keep in mind, it was precisely the reason we are in this mess right now.