"the houses are just being built now.................so they wouldn`t really be dirty"
Your going to get a shock then when proper window cleaners turn up and its more than ten bob a house for an initial clean!
True. WFP will be useless. Every frame needs the stickers removed and every window will have atleast 1 sticker that will need scraping, not to mention the concrete. You will also have to battle with the landscapers who will be laying the turf and installing the fences around the feet of your ladder.
Looking at around 2 to 3 man hours per house on average, obviously more if there are more 4 and 5 beds compared to 2 and 3 beds.
Apart from that its great work
and you will pick up plenty of the houses as the homeowners move in.