House Upgrades

Upgrade	Unlocks	Cost	Storage Slots	Notes
Tent-to-House		5,000 Nook Miles
First House Payment	6x6 Grid Main Floor	98,000 Bells	80 Storage Slots	You can access storage by hitting the right button on the D-pad, and you can access the advanced decorating system by pressing down on the D-pad.
Second House Payment	8x8 Grid Main Floor	198,000 Bells	+40 Storage Slots
Third House Payment	6x6 Grid Back Room	348,000 Bells	+120 Storage Slots
Fourth House Payment	8x8 Grid Left Room	548,000 Bells	+120 Storage Slots	When you get your left room, you’ll also be able to start customizing the mailboxes and roof color of your house. To do this, just talk to Tom Nook about your house and select “I want to customize.” Renovations cost 5,000 Bells, and all changes will happen one day after you place the order. Tom Nook can’t do any housing renovations while your house in the middle of an upgrade. After you get your left room, you can also pick up your mailbox and move it. Just walk up to it and press Y, as you would with other furnishings.
Fifth House Payment	6x6 Grid Right Room	758,000 Bells	+40 Storage Slots	Adding the right room also allows you to customize your interior doors.
Sixth House Payment	10x6 Grid Second Floor	1,248,000 Bells	+400 Storage Slots	Adding the second floor will also allow you to customize your home’s siding.
Seventh House Payment	10x6 Grid Basement	2,498,000 Bells	+400 Storage Slots

Once you pay off your final home loan, you’ll be able to make changes to your house’s exterior once a day for free.

Nook Shop Upgrades

The day after your initial loan has been completed, walk into the Resident Services tent and speak with Timmy & Tommy. They’ll let you in on their enterprising business plan to open their own Nook’s Cranny shop on the island. To build the store, you need to collect 30 Wood, 30 Softwood, 30 Hardwood, and 30 Iron Nuggets crafting materials. (Source: https://animalcrossingworld.com)

Expanding

• 29 days of active game playtime
• "Active", meaning: if you're planning to commit some time crimes and engage in some clock-altering time travel shenanigans, you'll need to do it one day at a time
• For those who have lost all concept of time, your "days played" can be checked in the "Active Island Resident" task progress on your Nook Miles app
• 30 each of fish / bugs / fossils donated to museum (seemingly)

It will also take one full day in the game for the shop to be remodeled - during which time, you will be unable to buy or sell anything with Timmy or Tommy.