I will start analysis for the payment gateway development. For this analysis, I should need to know what requirements are required to create a payment gateway (for example: contracts, integrations, APIs, approvals, etc.)
Please take a look at our website for specific APIs that are relevant to your business case. https://developer.visa.com/
Since you're interested in payment methods, you can check out these APIs: https://developer.visa.com/site/payment-methods
CyberSource Payments: https://developer.visa.com/capabilities/cybersource/docs
Visa Checkout: https://developer.visa.com/capabilities/visa_checkout/docs
Visa Direct: https://developer.visa.com/capabilities/visa_direct/docs
In particular, see the top few paragraphs that are shaded in yellow that discuss the requirements to use Visa Direct.
After having read the documentation, if you meet the Visa Direct requirements, then please click through the link in those paragraphs to the Visa Direct Program Implementation Questionnaire, fill it out, and submit to the email address listed on that form.
To get started with Working with Visa APIs, click the link below to register and create a Visa Developer application.
This guide walks you through the key steps for application creation, credentials, and connection validation.
If you are ready after testing your App in sandbox, send us a production request and we will evaluate your Application and other credentials.
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Obtaining the actual software to operate as a payment gateway (either by licensing or having it coded specifically for you
Establishing a Official website partnership with an acquiring bank who will issue merchant account (for use by your merchants)
Establishing and maintaining PCI compliance.