None, it would help to have a degree in English, which means 3 years max, but that's it!
In reality you don't need to go to school to be a writer beyond high school. If you have the talent and can get things published you can write. Here's an idea. Go to college and major in journalism or English to help you become a better writer, but you can also major in something else for a profession and write on the side. That way you don't have to depend on earnings for a living in writing only.
they go to school for four years now.
2 years
seven years
you can do it after high school
8 years
9 YEARS
3 years
4 to 8 years
5 years.
12 years
2 years