Hi,
I feel sorry for the budget as this is not possible to make a payment processor like Paypal with in 750 USD. If you can make it more than 10 times then I may provide you the complete SRS of the system with the functionalities of the system.
Regarding the payment gateway, and the API documentation, I gone through is a processing system, which is having also its own bucket / wallet and would let users to keep it via card and process to other users. Receiving amount users and withdraw the amount if bank name is associated, hence Bank is your merchant too.
. It will include the following functional requirements:
1. User transaction.
2. USer payment
3. USer Chargeback
4. Merchant Transaction
5. Merchant chargeback and payment
If you have seen that I am not a robot bidder then we shall talk about the process flow.
Regards,
Mit-