In Beijing we have all kinds. People selling stuff, a couple of old guys accompanied by a boy or a girl who is carrying some kind of hi-fi playing some kind of "meditation music" begging, plain  beggars who just demand money, etc.

They dont want to work, so dont give them money.

i never saw that...never bumped into a seller in the subway station

  I've got a trick for dealing with street sellers who won't stop bugging you. It's only really the ones who manage to get at you when you're sitting outside, having a bite or a drink that become a real pain. They approach with their wares, you do the usual, "Bu yao. Wo shuo wo bu yao. Ni ting bu dong wo shuo shenme ma? Wo bu yao! Zou kai! WO BU YAO! ZOU KAI! NI XIANG SI DIAO MA!?! WO BU YAO!!! WO HUI SHA SI NI!!!" or whatever your particular appraoch is in this type of situation, but if they persist, I simply offer to sell them whatever I am holding. They offer to sell me a watch. I offer to sell them a half-smoked cigarette. They push the hard sell. I do too. It doesn't usually go on too long before they get the message and this way I manage to remain entertained and it's 'them' who become annoyed. Always works for me anyway.