[IrishRover]

I have a plan I'm going to be using shortly for something similar. The IRS!
It sounds warped, but hear me out.
The IRS deals with money in utterly incredible amounts--almost every dollar that the government spends is funneled through it. The opportunities are endless. Even a very short (day or two) delay in money transfer can be used to loan that cash out on various short term deals. Overpaid taxes that don't get reclaimed, etc. Other money can be siphoned of in more ways than anyone might think of--untraceably.
IRS auditors can haul in almost anyone, examine books for different companies in the course of a "random" audit.
Any concerns people might have about the IRS looking at them will be focused on the tax issues, not on some mystic conspiracy.
The IRS deals in some manner with everyone in the entire country-if they want a clandestine meeting, all they have to do is haul someone in for an audit. Their leverage is incredible if they want something to happen or not happen. And by analyzing money flow, they can find some conspiracies that way. They can also really impeed someone that needs it.

Then, in a secret facility or two, the real work of fighthing the supernatural takes place. They have the info to hunt down recruits, and the werewithal to take care of their people.