Paper Mario: The Thousand-Year Door Tips

Get rich quick
Go to Rougeport and go to the central part of town and enter the inn. There's a door that you'll hardly notice that leads out to the roof. Go out there and there'll be a badge shop you can't miss. Tell to the owner you want to sell some badges.

-this works great when you need to pay the gang of robbos to talk to Don Pianta