Getting cash isn't very hard at all. Depending on your level, you could easily just solo a boss for drops in mooshu, like the Jade Oni.
I personally don't think that they're very difficult, all you need is 2 people to beat them (I myself did it with a grandmaster ice and a lvl 32 death) and a good pair of decks that build off each other. I think that it is nearly impossible to solo them, as you would spend the whole time healing instead of getting in offensive spells.