When it comes to helping the homeless I pretty much go with the gut.
When I was around 19, was working at a gas station, this was a very busy street, so we got all kinds of characters... so I was always saying no to these people.
Anyways, this one guy comes up and asked for money to eat, there was a Denny's across the street and he was hoping to get a breakfast (it was really early in the morning) I was very hesitant, and all I had was a couple of twenties. I figured what the heck and handed him one, about 2 hours later he returns and gives it back to me. Manager gave him a job. I worked at the station off and on for the next 2 years and I always saw him start his morning shift. About the time I left the job, he came by and thanked me again, he had gotten an apartment, was getting ready to get a car, and was starting as a manager at another restaurant so I wouldn't be seeing him anymore... made me feel real good.
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You have to be careful about feeding a homeless person... me and some buddies were in Long Beach at a car show, I bought a couple of muffins at this one place, this guy asks for money to eat.. told him i didn't have any but I offered him a muffin, he took one and thanked me... as me and my buddies were walking back, he was bent over in pain, the muffin didn't agree with him...
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I live in a craphole town, lot of tweakers, I get asked all the time. I get the "ran out of gas story" and stuff like that... have not handed out too much but we have around 20% unemployment here, it's not a great place to panhandle because people either have no money, or it's really hot, or very cold here, so I am thinking quite a few are legit.