The entity that pays you. They may not be your boss, but you definitely work for them.
And the entity you pay? You may not be their boss, but they definitely work for you.
In a lot of non-traditional, professional relationships, it’s easy to get the “who is working for whom” mixed up. (Franchisee / franchisor, affiliate / brand, contractor, vendor, etc.)
Firing can go either way, of course.
But if someone is working for you (you pay them), treat them like it. Same for the other way around.