Are we in business or are we running benevolent societies?
The entire point of any commercial enterprise is to sell. YWCS had something of value, in this case job leads. He obtained them in the course of his business, so they were the result of his being a window cleaner and being perceived as such. In other words they were the result of his having invested time and money to be in the situation where he was, and so people made business opportunities available to him.
Someone else saw the potential of what YWCS had, and was prepared to pay to acquire that potential.
That's business.
It's not a moral, or ethical issue. If you recommend a tradesman to someone, it's not unusual for the tradesman to give you something of value for the recommendation, money or a free service (say one window clean) or a voucher to entitle you to money off goods or services.
Why is this any different?