Here are a few of the simple ways to get bells. which everyone can do very easy.
When you sell items, go to the Re-Tail shop, she offers better value on nearly everything. But don't try and sell trash.
Collect town fruit from other towns, and grow small orchards of their fruit to harvest and sell. (remember you can fit 9 fruit in each space in your pockets.)
Fish often, especially at the ocean or on the island.
catch bugs as often as possible.
Break the fake rock in your town each day and sell the precious metal or gems inside.
find and maximize the bell rock daily. (I dig 2 holes behind my character before hitting the rock with my shovel, this allows me to repeatedly hit the rock without being knocked back to far away. (Before "bell boom" you can get up to 8,100 bells. after 'bell boom' you can get 16,100 bells per day.)
When your finally able to, be sure to set your town ordnance to "Bell Boom". This increases the value of everything you sell, plus nearly doubles your daily bell rock output.