Agreed, unless there is a rule against the Winter Knight getting a salary from his Queen
... I seem to remember that there was a rule against him being paid, because Mab could have given him money then and didn't. Unless Harry just doesn't want to be in Mab's debt anymore than he has to be so refuses a salary.
I don't think there's any "rule against" salary, no.
If Harry had included a cash stipend in his negotiation, I don't think Mab would have blinked or balked.
But there
is now a rule against Harry being paid:
he didn't bargain for it... and Mab fulfills her bargains with surgical precision, and zero charity.
... Remember before the battle, Molly was buying a house close to her parents to further protect them and she loaned Harry her old place because he was homeless ...
I think Harry is morally/philosophically opposed to leveraging his power too-directly for wealth; it's a really easy line to cross, with a huge morally-grey area.
I
suspect this is a too-strict interpretation of the anti-warlock values that Ebenezer instilled.
Molly has no such inhibitions. She owns a luxurious condo in an ultra-secure enclave, paid for with magical service.
I don't doubt she has used her waywalking & veils & so forth to make her own wealth, independent of the Winter Court.
Like... in her "Ragged Lady" phase, she likely learned a bunch about the criminal underworld of Chicago. Returning to it as the Winter Lady, she could just walk into a drug-deal under a Veil, put everyone to sleep, and walk out with all the cash; or something similar in other places, where she doesn't bump against Marcone (but I suspect that during the Fomor build-up, his hold over all those street-deals was much weaker: killing one of those non-Marcone deals might actually
put Marcone in Molly's debt!).
Or just use a Way to courier some high-value deliveries with unmatchable-by-mundanes speed & security.
Or Veil into some top-tier business negotiations, and leverage that knowledge in the stock market.
etc etc etc.