do what i do
2 top windows = £3, if they are of normal size, and for 2 bottom windows = £2 you earn enough to wipe them over, and to be honest, if you have a snotter or sill cloth, i mop up, and wipe the frame when i wipe the edges, it take about 5secs more, and if you do a little bit each time, will save you more money over time, and earn you more than doing it as a one off.