Hi Simi,
double negatives can have two meanings: negative + negative = positive, or negative + negative = negative.
It all depends on stress and intonation:
- Again, tell me how much money you have...
- I said
I don't have no money... (<-- I don't have any money = negative)
- You
don't have no money, you liar! Come on, tell me, we need that money, man... (<-- It is not true that you don't have any money = positive)
Those two are pronounced with different intonation and different stress. I'm not sure how to explain it, mainly because I still really suck at sentence stress, but I think in the first "have" and "money" are stressed, in the second "don't" and "no".