If they're begging in front of a busy mall or intersection, I look to see what they do if someone helps them. I was at a red light and there was a homeless guy who was going from car to car. Someone in front of me gave him a burrito. He actually sat down and ate it so I knew he was hungry. I pulled up to him and gave him a banana. He politely thanked me for it. Seemed nice, lucid, and rational.
The fakers tend to be at the higher class shopping malls. I saw someone give one of the panhandlers an actual meal and she tossed it aside once the good Samaritan drove away. Others beg for food but still find money for a carton of cigarettes. Still others have track marks along their forearms, indicating heroin use.
Homelessness is generally not a moral failing. My family was very nearly homeless when I was a kid. There was a severe economic recession, my Dad was laid off, and then he had a heart attack. On top of everything else, we couldn't live with relatives because my extended family is all sorts of messed up (LONG story). And it wasn't just us. There were many good, skilled, educated people in my home city who just fell through the cracks. We eventually got back on our feet but it took time, and quite a bit of government aid, for that to happen. If it hadn't been for government support we might have gotten deeper into poverty or genuine homelessness, or we might never have gotten out of that.