Well one way to earn money fast is to go to the island at nighttime. Since you just got the game to unlock the island you have to pay off 2 home loans in your house. Then when you start up your game the next day Isabelle will say the old mayor is visting town today. At the island at nighttime there will be bug on the palm trees sometimes that are worth alot.
Goliath Beetle: Worth 6,500
Golden Stag: Worth 12,000 (Really hard to catch walk up to it as slow as possible)
Cyclommatus Stag: Worth 8,000
Horned Atlas: Worth 8,000
Horned Elephant: Worth 8,000
Horned Hercules: Worth 12,000 (Also really hard to catch)
On the trees in the middle the are also some bugs that are rare and worth alot.
Rainbow Stag: Worth 10,000 Rarity: Rare
Miyama Stag: Worth 1,000
Horned Dynastid: Worth 1,000
Oak Silk Moth: Worth 1,200
Saw Stag: Worth 2,000
Scarab Beetle: Worth 6,000
Giant Stag: Worth 10,000
Lantern Fly: Worth 1,800
There will also sometimes be butterflies at daytime
Emperor Butterfly: 2,500
Birdwing Butterfly Worth 4,000
Agrias Butterfly Worth 3,000
There will also sometimes be sharks at anytime of the day you tell its a shark because it will have a fin showing.
Ocean Sunfish: Worth 4,000
Shark: Worth 15,000
Whale Shark: Worth 13,000
Basically try to catch any fish fish with a really big shadow. It usually means its rare and worth alot. Try to fill up your box. You usually make 150-400k. Hope this helps! Source guide: http://moridb.com/items/bugs/ http://moridb.com/items/fish/