Well, it could be that Naruto, using his ninja skills and knowledge, takes over the criminal underworld to reform it. Maybe he uses his powerful jutsus to intimidate the bad guys into following his new rules.
Shikamaru could also be an ally. His intelligence would be invaluable in planning strategies and outwitting the more cunning criminals. He could help Naruto figure out the complex power structures within the underworld and come up with plans to either take them down or use them to Naruto's advantage.
He could meet some of Iwa's powerful ninjas. Maybe Onoki, who could either see him as a threat or an opportunity. There might also be some young Iwa ninjas who are curious about Naruto and his abilities.
He might meet some of his distant Uzumaki relatives. There could be elders or other Uzumaki clan members who have valuable knowledge about his family and their special abilities.
Maybe he's running away from the pressure in the village. There are always high expectations on him, and he might feel suffocated and need some time alone to figure things out.
Definitely not. Naruto is a character known for his ninja skills and his journey to protect his village and friends. A 'naruto runs a brothel' fanfiction goes against the essence of the character and the overall story. It would be a misrepresentation of the Naruto universe.
In this fanfiction, Naruto could also face challenges in running the clinic. He might struggle with administrative tasks since he's used to the action - packed ninja life. But he could hire some of his ninja friends to help, like Sakura as a medical expert and Rock Lee to handle the physical tasks around the clinic.
Often, there's the theme of Naruto using his ninja skills for good in the hospital. For example, his ability to sense danger could help in predicting a patient's sudden decline. And his strong willpower could be an inspiration for patients to fight their illnesses. Another theme could be the relationships he forms with the other hospital employees, some might be initially skeptical of him but later come to respect his abilities.
In a 'naruto runs a shop' fanfiction, he could run a pet shop. Naruto has always had a connection with animals. He rescues and rehabilitates injured animals and then finds them new homes through his shop. He might also have some special ninja - animal hybrids in his shop that are a big draw for customers.