Unfortunately Luke your first two questions are "how long is a piece of string" type. As a rule of thumb I calculate £1 per window (say £3 for a 6 panel bay) then add it all up and adjust it to suit my "gut feeling". This could be affected by access issues, proximity to other jobs, type of windows, condition of paintwork etc etc.
Only way to find out is to try - make a few mistakes and learn.
As to earnings - you could open a can of worms with that one
I would just say that after you've gained some experience and built a halfway decent round you should be aiming to turnover about £30-£40 per hour.
As always, that's "turnover" not "wages" - that depends on how much running your round costs you. Equipment, insurance, vehicle, office, advertising etc etc.
Basic equipment, I presume you intend to start "trad" (ladder and bucket)
Get a decent 3.5m double pointer window cleaners ladder - if you buy from Midland Ladders you can get a pair of safety feet fitted, and a 2m single point. Then you need a couple of scrims, a couple of bits of terry towelling for mopping sills etc, a 14" applicator and sleeve, a 12" squeegee and a little (say 6") one for georgian squares and an oblong bucket and a scraper for the bird poop.
A bottle of decent household detergent (fairy) and away you go.
All you have to do now is learn how to use the tools and find some customers - that's where the fun begins
All the equipment can be bought on-line from a multitude of suppliers, most of whom you can find by doing searches on here.