Great ideas!
It seems so obvious to use other skills to find the mark but it never occured to me. A thief could use a Gather Information check to find out where the best part of town is to pick pockets or what guards are willing to look the other way etc. Then he could use spot checks to notice bulging pouches, a gem being slipped into a pocket, or he can use listen checks to hear what amounts of money are being exchanged. As far as DC's for these spot and listen checks, I will need to look into the skill descriptions to get an idea but it shouldn't be too difficult. I think I'll scale the DC of spot or listen check to how much money is changing hands. People with a lot of money tend to keep it a little more secret.
SylverFlame, it does look like you have less money in your campaign but I like the idea of at least setting up some kind of chart based on class or rank. I also like the idea of using how much you beat the DC determining how much money you get.
Thanks for the great ideas!
If anybody else has something different or is using something like the above but has more detail, please share it.