Bells return as the primary currency in Animal Crossing New Horizons. They are needed to pay off the various loans you'll get from Nook Inc., and to purchase certain items. In general, there are many ways to obtain ACNH Bells in the new field of vision.
There will be a bell wallet in the place where the island is dug and glowing, and this wallet will become a cash cow. You can sell fruit on your friend's island, as long as it is not local fruit, you will get a considerable income. You can also mine rocks, feed small animals, etc. In short, as long as you take the time to do your work, you will definitely be rewarded.
I am not sure how many people are willing to spend a lot of time on tasks. Personally, I will choose to Buy ACNH Bells on the website, because I want to spend more time on building my own island.