A little confused. Aren’t contract cleaners/window cleaners mainly involved at the end of construction, ie when most of the risks (and reason for protection) have ended.
I do realise that some contract cleaners with direct relationships with builders may be involved very early in projects, but would not have thought these would be your ideal market.
Membership fee, what would this be for?
Cant quite see it with the groups you are aiming for, but perhaps I am mistaken.