This is a copy/paste that I found online googling for prices.
Move-In: 5,000 Nook Miles.
First House Upgrade: 93,000 Bells – Makes your tent into a house.
Second House Upgrade: 193,000 Bells – Larger main room of your house.
Third House Upgrade: 348,000 Bells – Adds an additional room to your house.
Fourth House Upgrade: 548,000 Bells – Adds an additional room to your house. Also unlocks House Customization.
Fifth House Upgrade: 758,000 Bells – Adds an additional room to your house. Also unlocks Door Customization.
Sixth House Upgrade: 1,248,000 Bells – Adds a second floor to your house. Also unlocks siding and mailbox customization.
Seventh House Upgrade: 2,498,000 – Adds a basement to your house. Also unlocks free exterior renovations for life when paid off. This is the final upgrade you can unlock.
It's okay. X) my friend and I are getting the games super soon and we've been gushing and looking up tons of stuff. I was just curious about the order.