Your house in Animal Crossing: Wild World is where you save the game, sleep, decorate, listen to music, entertain guests, and so on. This guide will outline the basics of everything you should know about your house.
When Tom Nook gives you your house, he isn't really giving it to you. What he's really giving you is a huge mortgage to pay off. But if you do pay it off, your house gets expanded into a bigger house... and you get a brand new, bigger mortgage. Eventually, though, after paying off loan after loan, you reach the biggest house, pay one final loan, and then that's it: you officially own the home.
Your house starts out having one small room, as well as the attic where the bed and phone are. As you pay off your mortgages, you get rooms added to the house. After paying off the first mortgage, your one room gets bigger, then after that, each mortgage adds a new room. There's a left wing, right wing, back room, and second floor that eventually get added.
Without furniture, your house will look pretty dull. Therefore, you'll need to go to Tom Nook's shop and buy some furniture. You might also be able to get furniture by popping balloons that float across the sky, or by shaking trees, by sending letters to neighbors, just to name a few examples. However you do it, get some furniture and customize your house. If you sign up with the HRA, you will get rewards for having good interior design. There is also the secret art of Feng Shui, which provides certain benefits if you put your furniture in places that give you good Feng Shui. If you master it, you will have good luck, and will get rewards from the HRA for good Feng Shui in your house.
Sometimes, a villager will ask you if he or she can come over to your house to visit. This improves your friendship with that neighbor. But be sure to be in your house and not blocking the entryway at the time that you schedule for your neighbor to come over, or the neighbor will later tell you that he or she came over, but you weren't there. That isn't good for your friendship.
There are occasionally events like the Flea Market that will cause your neighbors to randomly enter your house.
One of the things you can do in your house is watch TV. Maybe it's not that exciting, but it does have different shows on at different times. If you catch the weather forecast, you can find out what the weather will be like.
If you haven't played Animal Crossing in a while, your house will be filled with lovely swarms of roaches! You will have to run after them and step on them to kill them, or otherwise they will just keep scurrying around, which is gross.