I personal think window cleaning is more suited for the sole trader. When or if you are a larger window cleaning company and VAT etc comes into there really isn't a whole lot left in my opinion to start paying a franchise company a percent of profits, so I would say it will stump the growth of your business giving you an extra expense you don't need.
That is why I think so many people comment on fish window cleaning and there employees making very little money. Which becomes even worse when the sales people try to force there way into an area and undercut others, only tightening there own belts.
I once read some where on-line who was basically giving them a bad review after his own experience and someone else responded, saying "you have to work hard etc, I have a WC franchise with fish window cleaning and after four years hard work, I have now started making a profit.".
Feck that, four years without profit, it was hardly selling there positives. I would further speculate that most who may have failed with a franchise like fish window cleaning may have did a better job themselves.
People who a really serious about making a go at something should do there homework, run some figures together, you see so many new starts on here asking how much so I charge. how much do you want to earn? how much are you going to have to payout, how many customer do you think you could do? after that its just simple maths.
I think franchises like greggs etc. are very different, as they have there own recipes etc., that make selling there product easy because it has been tested in the market. Window Cleaning is a simple service that with some practice can be done quickly using professional tools, and is relatively easy to make money at if you do your homework, so why would you need a franchise. They are suppose to do something for you that would otherwise be difficult on your own.