It is customary, especially for new clients, to ask for an upfront deposit, then the bulk of payment upon delivery.For random internet clients I always ask for an upfront non-refundable deposit.
If it is a larger projects, I ask for 33% up front. Then another 33% upon delivery of mockups. Then the remaining 33% upon delivery of the work.
If it's a smaller project, I ask for 50% up front, then the remaining 50% upon completion.
This way, if you do get ripped off, you only lose part of the project revenue and not all of it.
Ultimately there are no rules for this. It's merely a matter of how you wish to handle it. You should also be very careful posting the same question just a few moments after your original question has been put on hold. Had I seen the duplicate I would not have answered this. Continually posting like that could result in your account being suspended.