[Presto]

A good way of making a lot of bells in a minimal amount of time is to travel to the Island, and hunt beetles and sharks. Once there, It has been recommended to chop down all the non-palm trees, and dig up the flowers. Then, plant some more palm trees by burying bananas. Palm trees will attract the pricey beetles. Chase away hermit crabs, and other crawling bugs, so that more beetles will spawn.

You could play the turnip market, but I, personally, find that boring.