Here's a link
roof cleaning company offering products for sale. and apply, also customer base for sale in selected areas
www.sprayandrelax.co.nz
I happen to know the guy who invented Wet and Forget, and also the guy who made Spray and Relax.
Wet and forget came first, he was a house painter who used a chemical to pre claen roofs etc. he then started diluting this chemical with water, bottling it, and selling at a massive profit, he is now a multi millionaire, no more house painting, and has developed other products also.
Then came the guy who made Spray and Relax. He decided to sell his product at around 1/2 the price, and also it's a more concentrated mix. So a considerably better deal.
However Wet and Forget is still the dominant market product, as they have the most catchy name, and a huge advertising budget.