window cleaning is deffo an unskilled job.
round management takes ten mins every night, custy relations just requires you to work with a smile and establish a few simple rules, tax and accounts is no effort if you have an accountant, h and s again takes a bit of reading or a one day course.
Cosh and staff management are the only ones where it can be hard and you have to be able to deal with a bit of stress.
Yu rarely have to use your brain with window cleaning, the hardest problem solving you have to do is work out the best place to park your van. I cant think of any jobs where the gap between money earnt and skill required is so vast. You can earn more than teachers, policemen, electricians, engineers etc.
When i worked in a call centre for 6.50 and hour I needed more training then i do for running my own window cleaning business.
What you do need is confidence and belief in yourself, and drive. When I look at my friends who are mostly highly educated and highly skilled, the reason I earn more than most of them is because i can get out of my bed every day without the threat of a boss shouting at me, and i can trust in myself on a sunday night that by the end of the week i can earn the money needed to pay my bills relying solely on my self