Paper Mario: The Thousand-Year Door Tips

Secret Badge Shop
When you enter the main or middle part of Rouge port, go to the rest house (it has a picture of a bed on the building) and go up the steps.

When you get up there, there is a secret door on the left side that you can hardly see. Go through it and you will be outside on the roofs of houses theres a badge shop up there (you can't miss it). Make sure you have a lot of coins because there expensive.