Having an ecommerce website can help you earn an income online. There are a number of different payment gateways that you may choose to integrate such as Stripe, PayPal, Apple Pay etc. All of these have different payment terms and ways in which you will receive the money. It is vital that before you set your ecommerce website live, you have checked that the payment gateway is working as it should. You can usually put the payment gateway in to test mode to check it uses fake card numbers. This will allow you to completely check the check out process and also email notifications etc.
IF at all possible, it is advisable to do a real purchase via the system. You may set up a product that is only a pound or so to allow you to make the purchase through the site. This way you can see what happens to the money afterwards and how long it takes to hit your account. IF there are any issues that arise at this point you then have time to rectify them before the site is set live to the general public, which could save you a lot of hassle in the long run.