There is a window cleaner knocking on doors taking money in advance for a block package of weekly cleaning up till Xmas, saying "I'm doing a lot of your neighbours". I said I'd never give money in advance and he agreed to come back today and do them the first time so I could see how it went. He's an hour late so I can only assume it's a variant on the old door-knocking scam. Obviously you should never give money in advance to someone you've just met, and a claim that he knows your neighbours should first be checked with your neighbours.