The Horror Condo is one of the places in Mario Party Advance that is located in the Horror Area of Shroom City. This is one of three areas that have more than one quest to do, in this case one for the Basement, 1st floor, and 2nd floor.
Down in the Basement, the player will find a few Lantern Ghosts watching a Toad Force V cartoon on a projector. One of them spots the player and asks if they are a fan of Toad Force V. His quest, Nerd Force V, involves getting a Toad Force V figure to be part of the club. The player must travel to the Item Shop in town, and get a Toad Force V figure from Paratroopa. If the player returns to the basement and shows the figure to Lantern Ghost, he'll keep it for them in exchange for the Gaddget, Poochy Pal.
Ninji bunks out on the 1st floor. He is also a fan of Toad Force V, and his quest, DVD for Me, involves the player getting a special and very rare DVD of Toad Force V. Only Mushbert has such a DVD. The player must go to the Mushroom Condo in town, and talk to Mushbert on the 1st floor. He'll give them the rare DVD (but he has 49 more of the same one, so he's not that bummed out). If the player returns to Ninji with the DVD, he'll mention that there were only 50 of these rare DVDs, then rewards them with the Gaddget, Tile Trial.
Finally, up in the 2nd floor, the player meets Mr. E, who is talking to Snifit. In the quest Condo of Mystery!, Snifit says that the condo is haunted, but the ghosts who haunt it have not been around. Snifit asks the player if they could get them for him, for they have not been getting along lately. The "ghosts" Snifit is talking about are the Boos from the Boo Cemetery. Go over there and talk to them. They will leave to haunt the condo. If the player comes back to the 2nd floor of the condo, they will find Snifit and Mr. E being haunted by the Boos. Mr. E runs away, then Snifit rewards the player with the Gaddget, Porta-Gust.