How exactly does Fiverr-style monetization work?

Question

Freelance

There is a need to figure out exactly how the monetization structure works, when any exchange takes% of the service, and not for a pro account.
With a pro account, everything is simple, there is a subscription and you pay for it. On a fiver, you first throw money into the service (as a customer), buy the service, the service takes it for itself, and then gives part of the money to the contractor (upon completion of the work), and keeps part of it.
In general, it is clear how it works, but the most important nuances are incomprehensible. Does anyone know and can help with this issue?
Namely:
1. How difficult is it technically? From the point of view of the implementation of such a model.
2. What is done if, according to the customer, the service is not provided in full, and the freelancer believes that he has done everything that is included in the scope of work? Need intra-platform arbitration? Money is not returned by default? Every conflict for 5 dollars is sorted out by the exchange?
3. And if anyone knows how complicated everything is from the legal side, so that the service can keep money on its own (for example, a freelancer turns it into his "candy wrappers" currency, I believe that a refund, although possible, is not expected )
For the future, I will be very glad if someone finds the time to answer in a detailed and accessible way, a hundred times better if there is a specialist among you who has dealt with such things. For the future, consultations and possibly assistance in work would be very useful (for a fee, of course)
Thank you! If I'm not clear enough, please ask.

Answer 1

1 easy, no more complicated than a subscription
2 depends on the rules of the platform, on the same upwork, the hourly work is guaranteed to be paid once a week, you can’t dispute it if you worked. usually arbitration costs money, in my opinion, they took up to 30 percent of the money for arbitration.
3 depends on the country, there is a certain limit on how much money can be stored, the same upwork automatically withdraws money to freelancers, the hourly rate generally automatically fights with customer credit cards without storing money at home.