In the beginning of the game, theres a great technique you can use to make cash. Head to the empty fields all around you to gather bamboo, leaves and flowers. Collect as many as you can each day for a week (you should be able to collect ten of each per day if youre quick enough). Especially good places to look are to the left of Codys studio, around the dig site, around Galens house, or in the area where the Harvest Sprite Tree and Spring are.
Once a week has gone by, head to the shipment box before 5:00 and put everything you found during your expeditions. You can make 10,000 or more if you do things properly!