Tira here, from Shopify Support.
You can pay for your products on Oberlo and through AliExpress with different payment methods. Check out our help doc that covers how you can place an order, and how you can choose which payment method to pay for your products (step #3): How to Fulfill AliExpress Orders. Here is a list of all payment methods accepted by AliExpress, from their website: AliExpress: What payment methods can I use?.
Let me know if that helps!