Hiya, hows it gone over the 2 yrs since youve switched?
I would do both but perhaps concentrate on pressure washing if you know theres a market in your area for it, as in good prices. You will easily make your money back.
Rutland pumps is a good starting point. I believe around 1500 if memory serves well (or a bit more) will get you a good machine between 15 - 21 lpm with good specs, turbo and perhaps a fsc on top.
Then research well or try a course, but perhaps research and gain knowledge on the general cleaning part of this forum. Yet dont mention your a window cleaner lol, they tend not to like that.
I was thinking of gutter vac as I had an awkward gutter clean the other day. This particular roof over hang came out as far as the bay window and my ladders didnt have the height for that. (Whereas on normal house a stand away would have worked well.) Yet you then have to think of a power source if customers are not in and so a generator would be required which ups the price.