About 10 first cleans on run of the mill semis, so about £120 ish.
Half what you would do on a normal day is about right as not only longer to clean them but got to find the house, park the right way, knock the door, maybe a chat etc.
I personally don't charge extra because I want the job. When I've tried to charge double in the past it puts a lot off. I'm actively looking to grow so a first clean is an investment in time that hopefully you get back down the line but as we know it's not always the case. I would charge double if I wasn't arsed whether I got it or not and I will do occasionally if they give the impression of being a messer.