Im going to start a clothing line soon. I want to use artist graffiti what would I need to do this?

That sounds like a great idea. It may be a little bit hard to manage at first, and you may need some money to start at first. Maybe, as the person before me said, join forces with someone who is experienced and have similar ambitions. Find places where you could sell the first couple of clothes. Maybe like fairs or markets. You would first need to figure out the average sizes of who you are making your clothing for, as at the start you probably cant make to many unless you are confident they will all be sold.Places like Etsy may be good for an online place for clothing or Deviant Art for prints if you want to do that too.
Anyway, good luck! It sounds like a very fun thing to do. :)