How can comission avatar artists send a custom made avatar to a customer that paid money for it?

my friend runs a avatar commission business that does very well, its his only source of income. it is physically Impossible for him to get a regular job due to disabilities. the way he Uploaded avatars to accounts was by logging in to the customers account and uploading it from his computer. this was a godsend for people like me who have strict parents (im 18) who barely even let them have their headset, and won’t let them have a computer. He needs a way to send the avatar to his customers so that the avatar is theirs, and its on their account, and if the customer or the artists account gets banned, the other wont be affected. he needs a way soon or hes going to lose his house and be forced onto the streets. any and all suggestions are Welcome. Thank you