Beetles are still a thing in this game. However, they are only really available in the Summer and there isn't Tortimer Island in NH, so you may have to wait until July, unless you are fine with time traveling.
Here are some other methods:
- Keep valuable bugs and fish in your storage and sell them to Flick and CJ respectively when they visit. CJ pays 50% more for each fish, and Flick pays 50% more for each bug. So, a sturgeon, for example, would sell for 10,000 bells in the shop, but CJ would pay 15,000 bells instead. I personally like to keep bugs+fish in my storage that sell for a minimum of 1,000 bells in the shop.
- Keep an eye for hot items that Timmy and Tommy are buying. You can check hot items by looking at the store sign. When the shop upgrades, there will be two items a day even. These items are going to be craftable items. Sometimes, these items can be very valuable. I have actually gotten mermaid items show up on there quite frequently. Since these mermaid items require pearls (some pieces require two pearls) to craft them, the mermaid furniture sells for quite a bit of bells. When it is a hot item, you can get 20,000+ bells (pieces that require one pearl) or 40,000+ bells (pieces that require two pearls) per piece. Pearls are quite rare, so you will probably get most of them by giving scallops to Pascal. Sometimes he'll give TWO a day now with the release of the 3.0 Update. I personally have been giving scallops every day to him. Not only do I enjoy his presence, but I also like staying stocked up on pearls for days a mermaid item is a hot item. Other items still have a decent value too. Also, my brother got back into this game (briefly) after the 3.0 Update released and he mentioned making 400,000 bells in one go just by selling iron tables
- Turnips. You can buy turnips every Sunday morning from Daisy Mae (5AM to 12PM). It does require luck to get a good profit back, but if you have a NSO subscription, you can travel to other towns to sell your turnips at considerable profits. A lot of people on here even ask to visit towns to sell turnips, or even offer to let people in if they think they have a pretty high price.
- If you have the HHP DLC and design enough houses, you will eventually be able to convert Poki into bells. Unfortunately, however, you can only convert 15,000 Poki per day, but it is still a way to make a quick wad of bells.
Just be aware that the conversion rate does fluctuate day to day. Usually for me, the conversion rate is 100 Poki to 200-300 bells, so I usually get 30,000 to 45,000 bells per day by doing this. I believe it goes directly into your account.
- Money rocks. There should be a money rock on your island every day. Kapp'n tours will also have a money rock per island. With the 3.0 Update, you can now go on two island tours a day (though you have to progress to a certain point with the hotel). The first one will cost 1,000 Nook Miles and the second one will cost, I believe 100 hotel tickets.
- Bell vouchers. If you don't mind selling out some of your Nook Miles, you can buy Bell Vouchers from the Nook Stop. Each one costs 500 Nook Miles and sells for 3,000 bells. This means you are getting six times as many bells as you spent Nook Miles.
