dude don't be too quick to knock other people's opinion if it isn't what u want to hear, there's some good advice I've just read here. even if some is tongue in cheek!
if I were to generalize, I'd say the average window cleaner (if there is such a thing!)makes between 120 and 200 a day on average domestic work by himself. but don't think it's easy money, the higher earners have priced well, work hard, and refined their work over many years.
if you haven't done any/much you can't really knock anyone, or really know what to expect. don't have too high expectations is all, you will only be disappointed.
window cleaning can provide a good living with low hassle.but it's not for everyone. and there are still challenges. the better prepared you are for it, the better you will succeed.
oh, and good luck with it!