Back to the thread you bitching lot!

Natural progressions from Trad window cleaning, not including WFP are:
Gutter cleaning - buy a ladder stand off, some drain cleaning rods, a half moon attachment and a narrow trowel
Con roof cleaning - long car wash brush on a pole
Pressure washing - go for Honda GX390 13 hp machine if you can afford it, 5.5hp isn't up to some jobs.
Moving a bit more laterally you could go into:
Builders cleans - low investment costs - henry hoover, brushes, floor scrapers and some cleaning gear.
Carpet cleaning - high investment costs if you want to do it properly
Oven cleaning - - high investment and a pain in the arse to do.