How to connect a payment aggregator if I am not registered in it?

Question

Payment systems

The guys have never encountered this at all (with the installation of accepting online payments), but here the client asks, and I don’t quite understand how this process is if I’m not doing all this for myself?
On all aggregators now I read the steps, register ... send documents ... etc. etc. But why should I register if this is not my account, but the client's? How to install on someone else's site? I’m reading the same SimplePay right now: “Register on our website to get code examples, modules and documentation”, and in registration: registration type, individual entrepreneur or legal entity, etc. WHY DOES MY CLIENT ASK FOR YOUR DOCUMENTATION? He is not familiar with html either. Am I supposed to register myself or what? Or does the client have to give me the password from his account in the aggregator chtoli? What is the order?
And if it's not difficult, please tell me some not very difficult to install system for receiving payments on the site WITHOUT CMS, i.e. with a simple API and with the requirements of a not very huge package of documents for the site owner. In fact, you only need to accept visas and mastercards from cards. And in general, is it worth trusting everyone in a row, or only large ones (walletone, for example)? Has it ever happened that the aggregator took and disappeared, or simply stopped paying? I’ll install it for the client, and then he will say why he installed the charlatans for me))))

Answer 1

1. Register for a new e-mail, report this data to the client, forget it yourself later.
2. Or let him do it. But he still has to tell you the password during debugging, so what's the difference.
3. You need technical documentation. But in order to start using it, you will need to register in order to get a key, etc.
4. As an option, you can register yourself, do everything, check. Then the client registers and you just change the key in the system you wrote.
5. Acceptance from MasterCard and VISA cards is a banking system. You'll have to sign a contract. Send an agreement, put stamps, receive an agreement from the payment system....
6. I use Payonline (not to be confused with Payoneer). The API is quite simple (although it seems to be intricate, but as you figure it out, it is clear that it is both convenient and minimalistic and universal).
7. Waletone - small
8. You can check who has a direct contract with VISA and MasterCard - this is a lot of money and the company will not disappear so easily. Such firms once or twice and miscalculated.
9. There is not much risk. They all send loot within 3 days. If anything - in just 3 days there will be losses, no more. If the term for sending money is longer, then this is suspicious.