If you mean upgrade, (bigger room, basement, upper-floor) then for the Animal Crossing that I know of, you have to pay off your house.
To do this you go to the post office and ask to "Deposit". It generally tells you how much you need to give until the next upgrade.
im trying to do the same thing i have no idea
Her house does not exist at this time in any Animal Crossing game .
Edit you're wifi settings
You can't. Resetti's house is only in Animal Crossing City Folk.
No, but Animal Crossing: Wild World you can get a AR DSi and get infinte bells.
Nope.
Ya! Your house in animal crossing wild world can hold 4 pepole!!
No you cant
No.
A mansion.
buy a house
no, it can only get bigger
No. Same apply to all Animal Crossing games and Pets outside of the house and cage (tank).