Playing Rise of the Runelords...
SPOILER
...and the players just got to Magnimar.
The halfling rogue started lifting wealth off of the people at the bazaar.
Now, of course there's the risk of getting caught but the dice are really really s@!%ty for our dear rogue, and quite stellar for the onlookers, most of her victims, and the people in the immediate vicinity, stand little-to-no-chance of spotting her pickpocketing.
Now I actually don't mind this. The character is an excellent thief, who picks her marks, watches them closely, waits for the opportune moment, and then steals their cash.
The question is... stealing from the wealthy merchants and nobles who frequent "The largest free market in Varisia", should bring in a pretty penny.
But how much?
your thoughts are greatly appreciated.
Thanks in advance.
-Nearyn
Decide the NPC's level, check the wealth of any given NPC at that level, and cross-reference that NPC's lifestyle (I think that chart is in the GMG, but you can find it on either of the SRDs).
Based on that information, I'd make a small graph of NPCs at various levels and how much gold they might have on them at any given moment. Not ALL of their wealth is going to be in liquid assets; they will have homes, families, etc.
If I were to just ball park it, I would say that any Commoner NPC has their character level times 50 in gp in savings, and any fraction of that in their purse at any given time at the GM's discretion.
Allow the character to make a quick profit. Professional pickpockets can make a living of some sort, but none of them earn enough to buy magic items. When he's made a few little scores, make a not-to-subtle hint that he'll be attracting attention very soon and people are going to notice their coin purses missing.
The gp amount is up to you. If he wants to make a career out of it in a huge market, have him use it like a profession check, but with the chance of a critical failure on a 1.
Take a page from Tolkien... one of those insanely wealthy merchants has invested in a level 2 spell... Magic Mouth cast on his purse and set to start screaming "Help! Help! I'm Being stolen! Thief! <NPC Name> is being robbed! Help! I'm being stolen!"
After finding that there is an actual risk, I think your PC may well move on to easier pickings. In a fantasy world where magic is common place there isn't any reason for the wealthy to walk around with their money unprotected.
You could run it similar to the Profession skill and figure out how much money he could make in a week doing that.
Thieves’ Guild (4 PP): Nearly every community, from
the smallest village to the teeming metropolis, has a
criminal underground, and most have one or more
thieves’ guilds to look out for the interests of those on the
opposite side of the law. As a member of one such thieves’
guild, you gain a +2 circumstance bonus on Sleight of
Hand checks to steal items without being noticed. You
can use Sleight of Hand to make Day Job rolls.
Day Job Check Rewards
DC Result GP Award
5 1 gp
10 5 gp
15 10 gp
20 20 gp
25 50 gp
30 75 gp
35 100 gp
40 150 gp
One thing to remember is that realistically most of the people in Ye Olde Fantasy Market aren't going to be carrying gold coins, they'll be carrying copper coins mostly, and some silver. Gold coins will be rare and probably held far more closely than in your standard belt purse, increasing the difficulty.
Also note that a lot of the locals will have arrangements with a lot of the merchants: put it on my bill and I'll settle up at the end of the month. It's only poor credit risks like adventurers who need to pay cash on the dot.