1. You HAVE TO pay the Aliexpress seller via Credit / Debit card. It's only way.
2. If a customer pays via Paypal ... you have to transfer the money to your bank to pay the Aliexpress seller. That can take up to a week. You can't pay the Aliexpress seller with Paypal.
3. If a customer pays by credit card ... it will take up to a week for the funds to be transferred to your bank account by the credit card processor.
Either way ... you do not get access to the funds for up to a week.
You can not expect the customer to wait an additional week. The shipping times are already slow enough. The customer may not come back and/or will be sending you lots of emails complaining about the waiting time.
Because of this ... you need to have a couple of hundred dollars in your bank account when you first start so you can process the orders IMMEDIATELY.
If don't process orders immediately and force customers to wait an extra week ... you will lose customers and your web store may fail.
But that's totally up to you. If you want to make customers wait extra and piss them off, do that. My advice is NOT to do that and save/beg/borrow or steal a couple of hundred dollars to start you off.