I'm not sure, but I think you need a high stealth level to pick pocket. I used a cheesy technique to get all my abilities to 100. ***Spoiler***
I use a lower ability spell on myself at a trainer in that ability. The spell only lasts 2 secs, but it lowers my ability by 90 points. I immediately open the dialog with the trainer and since my skill is so low, he trains me. The spell expires and my level is up one level from the original. Repeat to level 100.: 
Even with 100 stealth, I get caught about 1 in 4 tries.
Try the money making schemes in this forum. The potion scheme is effective.