Coconuts are worth 500 bells to Tom Nook so getting your hands on them can be very useful. They will wash up on the shore from time to time and all you have to do is go over and pick them up. But you can also plant them.
When choosing a spot to plant your coconuts be sure to pick a location near the beach. Palm trees will not grow on other locations of the map so do not stray too far inland.
When the trees grow up they will produce 2 coconuts at a time which will quickly add up to lots of extra bells which obviously comes in handy for finding the furniture and other items that you are looking for.