Spirit Tracks How Can You Get a Lot of Rupees BEFORE the Trading Post?

[CheeseXCrackers]

I'm playing ST again and I want a lot of rupees but I'm not far enough in the game to use the Trading Post.

Is there a tree somewhere that has 100 rupees hidden in it? Something like that? I've been rupee grinding in the Tunnel to the Tower. Is there a better place to rupee grind?