A single entry-level red court vampire is not too bad, in part because their skills are not very high. (So they can be sloppy while still being dangerous.) Similar things could be said about ghouls and such.
But, hey: why not give your guys mortal adversaries, like a few common thugs hired by a mysterious supernatural "backer" to rough the characters up? They'll have to navigate both mortal law and the Laws of Magic to defeat these guys, after all, which is a good thing to cover while in the learning stage of things.
