What you need to think first about is, its your business that is at stake if you don't get enough work to survive on.
Any property with windows is fair game to be canvassed, if they have a window cleaner and they are happy with him then they won't move, if they are unhappy with him, then you might gain them.
I don't take on anyone because of price, I give my price and that's it, no "haggling".
With commercial work the rules do change a bit, because commercial work is normally bigger, the earning power can be higher than domestic customers, so competitive pricing is normal, on a lot of the tenders that I go for the cleaning budget is known to every company that is tendering, all you have to do is work out what you are happy with.
I don't take kindly to treats and if someone did telephone and got nasty then I would make a point of canvassing every single customer he has.
For dole cheats, why worry, one telephone call to the DSS and they are soon gone, if you think this is "grassing" and against your principles then don't complain about them working in the first place.