If your friend that is a window cleaner is making a descent living at that price in your market…
Then run with that pricing to start, but don’t limit yourself on what you believe some one will pay for your service.
I’m not sure how your setup business wise ( business lic,insurance, business cards, company apparel etc) or just flying by the set of your pants…
The more polished the appearance in
your gear and process of cleaning the glass the more money you can demand for your services.
(Especially when you service your future residential clients)
Hope this helps.