I hired windows cleaners when I first moved into my house. I used Squeegee Pro. Wouldn't recommend them. Expensive and the work was not very good.
The cleaning lady that we hired to clean our house offered to clean our windows for a much cheaper price, but I assumed dedicated window cleaners would do a better job. I was wrong. These window cleaners don't do anything special. They just clean the windows like a cleaning lady would.
I made an incorrect assumption thinking that these window cleaners would have special equipment to get the windows super clean. Nope. it's just windex and elbow grease. For some of the second floor windows, a ladder.