From someone (me)who started window cleaning 28 years ago (residential, post construction clean up) . It's easier for a window cleaner to transition into pressure washing and still do windows than a pressure cleaner that adds window cleaning on as a service and be successful . I have helped many over the years and pressure cleaners get to frustrated with the details of window cleaning. My personnel opinion from experience.
I make more money with a water fed pole than I do washing a house but that comes from knowing how to prep a window before the wfp and di water during the house wash.