You're gonna get busted or robbed if you're not careful mate. If you don't have connections already and go around trying to make them, chances are you will contact filth and/or villains at some point.

If you really want to sell on a large scale try buying small amounts and become friendly with the small time dealers. When you find someone you think you can trust (i hope you are a good judge of character), try getting intros to their suppliers and gradually work your way up. Just be subtle and don't try to fuck anyone over- remember you are dealing with criminals- its easier to rob you and take all your weed rather than buy it and sell it on.