House upgrades and mortgages in Animal Crossing on GameCube
Four upgrades, then a statue. The figures below are the constants the game compiles in, not numbers gathered from playthroughs.
Every payment, in order
| Pays for | Bells |
|---|---|
| Your first house Set the instant you pick a house. Nook quotes 19,800, then takes your 1,000 bells and counts 1,400 of wages against it. | 17,400 |
| First main-floor expansion Unlocks the medium house. | 148,000 |
| Second main-floor expansion Unlocks the large house. | 398,000 |
| Basement By far the cheapest room in the game. | 49,800 |
| Upper floor The last thing you pay for. | 798,000 |
| The statue Free. It is what you get for clearing the lot. | free |
Paying every one of them costs 1,393,800 bells after the first house, and the statue adds nothing to that.
The house grows when you finish paying, not when you agree
This is the part that trips people up. Taking on the next mortgage does nothing to your house. The room only changes once the balance reaches zero, and then Nook offers you the next one.
The game tracks five stages, and its own labels for them say so plainly: the starting size, then one for each debt cleared, then the statue. The upper floor is gated behind the basement as well, so the basement is not optional if you want the full house.
Practically, that means the cheap 49,800 basement sits between you and the 798,000 upper floor, and there is no way to pay them out of order.