believe it or not, public liability is not a legal requirement, but it makes sense to have it, and it isn't that expensive either.
Average amount of houses will depend on many factors.
But as an example:
a 3 bed semi, 4 windows on the front, including door, 4 on the back including a patio door, and 3 small windows on the side, including a door.
Providing they are standard type windows, and not of the georgian variety, this will take most window cleaners between 15 and 20 minutes
Most will be charging anything from about £6.50 to about £10.00.
You will take at least 3 or 4 times as long as this to do it to a professional standard. It will take a couple of months before you get up to speed.
It will take several months to build up your round, but once you are cleaning at the required speed, you should be earning between £80 and £150 per day.
It will also depend where in the country you are and the type of houses you are cleaning.
Bare in mind that you will only actually work about 6 hours in any one day, you may well be starting at 9am and finishing at 5pm, but productively you will only have actually worked for 6 hours.
Chatting to customers, drinking tea and coffee, loading and unloading, driving between accounts and so on and so on, will eat into the time you are actually cleaning windows.
Best of luck, and keep posting your questions on the forum!
Ian