One very helpful way to get even more koins then just the ones laying on the ground or in the already unlocked houses is. Right after you're done doing missions for the village where you start out in the beginning, you should be able to get out of the walls. The kid that can disappear (you could of done a mini-mission where you had to find him behind a tree in the first park)will be trying to rob an old ladies house near a patch of trees. Before he gets in there or hides in the patch of trees punch him. You should get a pick . Use that for locked doors.