I'd like to create a "shipping store" but I'm not quite clear on some things

[vmscissors]

One of my sales channels is wholesale which is not handled via Shopify.  However I've decided to offer a shipping service where customers can send their items purchased outside of Shopify to me for service & repair.  Once repaired or serviced, I can ship back to the customer.  I'd love for some sort of website to facilitate that for a flat shipping fee.  Can anyone recommend whether that would be possible?