Based on my experience, people tend to be more generous with you if you look clean and good than if you are mentlly ill on the street. When I begged for a hobbo fucked up to buy him falafel, in 2001, I was succesful in getting the money. When I pretended to be homeless in 2001 later, I was helped by a nice man who spent about 50$ on me that day for no reason. When I became really homeless, all my begging was pretty much unsuccesful. And I was invisible to society.