I was thinking about the gold the four Fighter Guild smiths have on hand for daily transactions, which got me to wondering - do they work for the Guild itself or are they independent operators who the Guild lets run their business on Guild property? The smith at Sadrith Mora restricts his business to those of a certain rank or higher. I forget how the guy in Vivec does business. The other two deal with anyone.

Is there any lore dealing with it?

I would assume that they're independent operators who are members of the guild. In exchange for being able to do business on guild premises, and have easy access to guild members, I'd imagine that the Fighter's Guild coffers get a 'cut'.

In other words, I don't think that they're just 'employees' working the counter like the cashier at Walmart or McDonalds. They're actual artisans, and members of the Fighter's guild, they just pay a portion of their earnings to the Guild...or maybe they don't pay at all. Who knows, I'm just guessing.