“I just have to have the ability for people to transfer their cash to a pre-paid card.”
Yes. You have to have the ability for them to bring in cash for their purchase.
To a machine that can issue a pre-paid card, that does not have to be part of the business. It just has to be onsite.
I can refuse cash in that situation and accept pre-paid cards, that are only good for my business, which forces the customer to have to spend the entire pre-paid card at my business.