front lawn

As I write this, there is a man in my front yard mowing my grass. I have no idea who he is or why he is doing this. Instead of being grateful, I am partly scared and partly annoyed. I don't know if this is someone who is a little crazy who does work, then rings the doorbell and demands to be paid. Or maybe this is a neighbor who has grown sick of my high grass and decided to take matters into his own hands.

I actually pay someone to cut my grass, but he is notoriously unreliable. But he is very cheap. He called me two and a half weeks ago and said that he would not be by on Saturday, unless I wanted him to come, because he did not think the grass needed cutting. We agreed that he could wait until the next weekend. It rained and the yard flooded that weekend. But this weekend would have been fine. For whatever reason, he did not come. Now the yard really needs cutting! For all I know, the guy in the yard might be working for my guy!

Several years ago, I hired a fella who was passing through the neighborhood ringing doorbells. He offered to rake leaves. We agreed on a price. He finished about two thirds and asked for the money. I gave him two thirds of the agreed upon price and never saw him again. The yard looked funny for weeks until enough leaves fell to fill in the blanks.

The lawnmower sound has stopped. Exactly what is the etiquette in this situation? If he rings the doorbell, do I have to respond?