The biggest half of my work now is large houses out in the sticks, but I also clean over 100 houses on a nice estate in my town, I started canvassing the houses here as soon as they were built. The other local window cleaners know this and refer any inquiries they get for work on this estate to me, and in turn I do the same for them on areas where I know they have a lot of work. It makes things work nicely between the local shiners, and helps to keep our rounds compact.
Sure I get the odd out of town window cleaner show up on my estate, I generally let them get on with it, and most of the time they soon realise that I have virtually all the work there and they go elsewhere, I only really get upset when they try to steal my work using dirty tricks such as telling people I have stopped working in the area etc!!