Ahahaha, wow, the first thing that came to mind reading this is how this kid named Thomas in my high school had been getting spooked for a whole month because this shoddy old man stands outside about a block away from school and keeps going "Help the homeless". Except the dude sorta mutters it and speaks fast, and Thomas kept thinking he was saying "Help me Thomas". Ahahaha, good times.
Anyway, I get a lot of those homeless people, living in New York City. There's a huge homeless population in the Subway system, and it's pretty common to have someone walk into the subway car asking for money. Honestly, I don't give unless it's very apparent that the person's in need of help. I've seen my fair share of tricksters. There was this one dude who was pretending to be blind and asked for money. I didn't give, but at the end, he made a whole dramatic scene where he was miraculously cured, and then ran off with the money.
As for street performers and Elmos, I've been on the flip side actually. Well, sort of. Times Square, at night, has these performers who break dance and then jump over people. I got to know a few of the people who did that and then got involved at one point, so I know how hard it is to actually make a decent amount of money. Doesn't help that the cops in Times Square are *****y when it comes to loud music. Anyway, I don't really give them much either, tbqh. While it isn't as much as one might think, the performers in the city do make a fairly decent amount if they work at it for a good amount of time. Outside the touristy areas, its a little harder. Hell, we even get performers in the subway, and it's hit or miss with them.