allot of those adverts maybe national window cleaners, or cleaning contractors that really isn't going to put too much of a dent in the resi work that will be out there. If you keep thinking when is the right time, is this the right place etc. you will never go for it.
If you put in more work, do a better job, earn a good rep and charge a reasonable price, how many window cleaners there is wont bother you, its what you do that really makes the difference not everyone else.