I have been using DBTech's shop and credits addons for years by this point, originally on vBulletin and now especially on XenForo when Decado, the Founder of DBTech went out of his way to manually include features such as multiple shop ownership, taxation and the ability for users to upload their own item images when he became aware that my community, then on vBulletin were feeling discouraged.
The Xenforo version of DBTech's Shop offering is without, peerless in this area. It makes multiple shop ownership not just possible, but fluid and seamless in its integration. Permissions on an item-per-item basis are robust and it is lightweight yet powerful.
It integrates nicely with Credits, and coupled with Xenforo's native trophy system, provides a fantastic achievements system that makes it worthwhile for your community to spend the time using it.