One possible storyline could be Naruto renovating the apartment building to make it a better place for the villagers to live. He might use his ninja skills to do some unique construction work.
There could also be external threats. Maybe other villains or rival ninja clans see the apartment building as a target. They might try to take it over or destroy it to undermine Naruto's influence in the village. Naruto would then have to use his combat skills and strategic thinking to protect his property.
Perhaps it's a community building. Naruto is a very community - oriented person. He could own a building that serves as a place for the villagers to gather, like a community center. There could be a cafeteria, a place for kids to play, and rooms for meetings and celebrations.
He could transform the building into a ninja academy annex. Naruto loves teaching and passing on his knowledge. In this annex, he could offer advanced ninja training, focusing on things he has learned from his own experiences, like dealing with powerful enemies and using the power of friendship and determination.
In the fanfiction, he might own a building that is actually a magical library. Since Harry has always been interested in knowledge, this building could be full of rare and ancient magic books. It could also be a place where wizards and witches from all over come to study and research, and Harry, as the owner, would be in charge of protecting these precious knowledge resources.
Well, he might offer ninja training. You know, teaching basic jutsu like the Clone Jutsu, or how to improve one's chakra control. It could also be about physical training, like the intense workouts Sasuke used to do.
He could turn it into a training ground for young wizards and witches. Teach them how to defend themselves against the dark arts, just like how he was taught at Hogwarts.
Maybe he gets a better apartment through his newfound popularity as a hero. People in the village might recognize his efforts and contributions, so they offer him a nicer place to live.
A common 2-story apartment building is likely to be about 25 feet tall. However, it can range based on construction standards and local building codes. Sometimes, taller ceilings or special architectural elements can increase the overall height.