to add more opinions to the pot. If you have to ask, you're not read to make money selling herb. You need the hookups, the capitol, and the customer base, and it's unlikely you have any of that right now (except maybe the capitol, but that is actually the easiest part of what you need). To get the supply and customer base takes real time. Most people who sell started out small. They were buying singles or quads, and realized that if they got an oz, and sold off a few singles they could smoke for free. Doing this for a few years, they met people, made contacts, built up customers who would regularly come to them, and instead of running out they just bought more (more free weed, score). At some point they find they know someone (or know someone who knows someone) who can get real volumes (lbs or more). and they have enough business coming to them for it that they can get rid of it in a timely fashion. They find they have more free herb than they could ever smoke, cook, extract, and just start selling it, and now they are making money, and if they have a good hookup and decent customer base, potentially a lot of money. This takes years, and unless you get really f'n lucky and somehow meet someone who can supply real quantity who is willing to even tell you they sell, it's not something you are going to just jump into. This is an illegal business everywhere in the US, and is treated as such. It's all who you know, and the people you want to know, unfortunately, don't like to get to know new people.
The only real sure fire way I have heard to test for narc's is to buy drugs off them and make sure it is clear you are planning on reselling them (I have been told this by a narcotics officer with my local sheriff, as well as by a defense attorney who specialized in marijuana defense). The one absolute in undercover narcotics work is that the government cannot become a drug dealer, they cannot release illegal substances back into the market. If an undercover sells to you and it is clear you plan to resell some or all of it, they will bust you before you get a chance to sell any, if they don't they just became illegal drug dealers and their whole case is invalidated. However, informants can do whatever the hell they want, so this only works on leo employed by the govt.
Personally I wouldn't want to be doing business of any quantity with someone I haven't known for a long time, and my connections when I used to sell were all developed over a 10-15 year period. I wouldn't trust someone who is dumb enough to sell lbs to someone they just met.