where would one pay the custom's clearance if I opt for the latter?
Firstly, always use a physical address, preferably at the office. Secondly it depends on what shipper is used. If Fedex or UPS then they will contact you for pre-clearance payment. If it's USPS or DHL Global then this is handled by the lovely Post Office and they will expect an EFT when they arrive at your office.
Have fun.