Going with the "using a daughter for a plan", there's an old Mercedes Lackey book where there's a elf lord with a half blood mortal daughter. The lord is unseelie and a big nasty and at one point his daughter says "Look, there's no profit in that - we aren't doing it". Then her father took control of her, and her mortal magic (a different flavour than elf magic, able to do different things) and made her body do exactly what he wanted.
How?
Back when she was too young to know any better, he cast spells on her and made deals with her. When a father asks a 4 year old, or a 5 year old, or an eight year old "Will you do anything for me?" he's going to get a "yes". If he phrases it right (and what centuries old manipulator couldn't do that?) so he can get her to agree to what he might need her to do then he can get the kid to agree to practically anything and then 20 or 30 years later call enforce the agreement.
Which is a very nasty thing to do to a PC - but a great hook for an NPC villain. One who doesn't want to hurt people or break the laws of magic, but back when he/she was a kid good old Uncle <blah> got him/her to agree to things and it turns out that Uncle <blah> is a fae or other creature of the Nevernever. Now he/she has to commit those crimes because Uncle <blah> asked "If I buy you an ice cream, will you help me take over the city?".
As for a source of resources - I can see any sidhe getting all the money he wants. Would a billionaire pay a million dollars so his daughter would look perfect for her wedding day? Would another rich man pay $$$$ for the ability to play an instrument/paint/dance/whatever at a world class level (like those poor mortals in the Winter Court swing band Harry stumbles over when he first meets the winter lady)?
And how about just tricking people - Bernie Madoff swindled billions without needing Fae magic to do it. A good con job can take in $$$$. In fact, here's a real life example of one that might get hundreds of millions -
http://en.wikipedia.org/wiki/Office_of_International_Treasury_Control - which (according to one source I found) seemed to be revolving around getting memorandums of understanding on deals worth billions and then getting loans (or selling privately placed bonds) backed by those agreements.
Since money matters to mortals and not to fairies, I see the Winter and Summer courts having slush funds. A "You want to pay some games with the mortals? Here's some money. Do you want a hundred dollars? A million dollars? Take what you need" type fund. Maybe only only the nobles would have access to it, but I can't see the Lady of Summer having to run a con job to stay in that hotel in Summer Knight.
Richard