No, The First Slam Dunk is not based on any real-life character. At least not confirmable by the author. There was an urban legend about a picture of Hanamichi Sakuragi. However, it was later confirmed on multiple Reddit and other social media platforms that the picture was actually a member of a band named X Japan.

Manga author Takehiko Inoue was inspired to write based on his high school years. Inoue was inspired to create Slam Dunk from his love of basketball since his high school years. After Inoue began working on Slam Dunk, he was surprised to receive letters from readers who began playing the sport due to the manga.