I don't doubt that there are people who start dealing in exactly that fashion, I just don't think it's the most common way. Looking back at the article however, I see you said 'many' and I probably read it as 'most', so we're probably both right.
As for my use of necessity, I certainly don't mean to excuse their actions -- perhaps 'believed necessity' would be more appropriate.
Last thing, I was also speaking specifically to what I know of American drug dealing, and I have absolutely zero knowledge of how well that information travels overseas.
I think pleading "necessity" sounds like excusing the actions. It's very very rarely neccesary to have to deal drugs or similar to stay above the poverty line. Especially here in the UK where unemployment benefits are fairly generous. Unless not having the latest pair of Nike Air Max equates to poverty.