I bet we all thought window cleaning was going to be a simple business when we first started, and to be fair, compared to say being a builder, I reckon it is. We're not awaiting delivery of materials, dealing with their delays, dealing with surveyors and coping with all sorts of unexpected problems such as incorrect geological information when (for example) digging foundations and instead of finding clay, hitting rock.
It's a low cost business to start up in, and anyone can actually clean a window, even if it does take a long time to do it.