Ive asked myself the same question, and my conclusion is this.
The companies you mentioned have grown very quickly on the back of franchising (in most cases). Would you pay a franshisor say £25,000 for a territory of say 5000 homes, they tell you how to canvass it, give you a brand new sign written van, fully equipped etc etc. You then go out build your business and then pay them a fee of say 5% of your gross revenue.
Say you build up a business with a turnover of £52,000 pa. The work is 4 weekly on average and takes up 5 days a week of your time. It gives you a net income of say £40,000 pa . Less your living expenses say at the end of the year you net £15000.
After your first year youve laid out £25k plus 5% of your gross (£2,600) Repay £10k of your initial investment leaves £5k.( you can work somewhere else without the hassle for more )
So you think sod this no return on my money Ill sell my business, say its worth 3x monthly income £12,000. Not very much eh!!
Who would lend you the money to buy a business that you cant maximise value should you wish to sell or when you want to get out?
Who would want to pay out £25k for something they could do themselves for a fraction of the money???
Who would want to invest money into a business that every tom dick or harry gets into when they need a few extra bob and dont mind working for £7 an hour?
However wfp may change this situation, because your business is no longer restricted to windows, there are a host of other exterior surfaces you can now clean, I think its these other services tied in with the regular window cleaning which offers real potential in this business. Exterior house maintenance, all that needs to turn up is a product that can be applied to clean upvc that gives it a gloss finish and protects it for a reasonable period of time, maybe 3-12 months.
Mark