Good citizens?

I woke up this morning to find out there are people all over our street. I was trying to figure out what they were doing. It looked to me like they were cleaning other peoples houses. There were teenagers with rakes and adults with hammers, little kids wiping windows. To me this was amazing. People that I've never seen getting together to help their fellow man. Maybe they knew the people on our street, for they never came to our house. It was alright with me if they didn't come. A few times I felt like I should go out there, ask if I could help do anything. Being me however I got shy and didn't want to bother any of them. It would have been great to leave it at that, people helping others for no other reason than to help, until my dad got up and as he was leaving to go to work he said; if they come to our door and ask if they can do anything, tell them no. I thought that was a bit odd so I asked why I had to say no. He turned to me and said you can say yes if you want to pay for it. It dumbfounded me. I never for a minute thought that these people were doing all that for money. Maybe I'm naive. Maybe I want to believe there's still good in people. I don't see anything wrong with that. But was my dad right? Were they doing this for the money, or for the sake of helping someone?