Tolzy,
I've just read your backposts and see you're new to window cleaning.
If I were you, and wanted to play safe, why not buy the guy's domestic window cleaning work?
Personally, I reckon (in my humble opinion (and it is humble; I'm not and never claim to be one of the 'high flyers' here)), that domestic work is a safer bet than large commercial work. In the past three months I've lost a large chunk of the small amount of commercial work I had; and I know there's other stuff I clean that's 'on the line'.