I want to become a homicide detective, can anyone help?

I am interested in becoming a homicide detective without connecting to the police department. I am in high school going into my 10th grade year. I would like to know if there are free online stuff i could look at to help. I know school classes i can take. But in the long run i know that i wanna open my own P.I agency and work out of the police department or with it, but not attached. Is there any way i could do this? Are there any online things i could look at or will studying mystery novels help me? Any tips or anything else i can do? Please provide sources for this question!