If it's only going to be used for window cleaning then get a 3.5m A frame ladder from middland ladders or Ramsey.
Designed solely for window cleaning the best ladders out their.
I fully endorse the above
Comments from an old dinosaur:-
The original 'window Cleaner's Combination Ladder' was manufactured by Shaftesbury Ladders, was a wooden 'A' frame with a splayed bottom section that could also be used as a step ladder, hence the 'combination'. It was designed by traditional window cleaners who wanted a versatile, safe ladder for use in all situations.
Modern aluminium window cleaners ladders retain all the features of the original 'com' but are much lighter and more durable. The main feature is that these ladders can be set firmly in situations where the ground is not at right angles to the wall and can also be used by putting the point into the side of a window frame, cleaning halfway across then moved to the other side to complete the job. This overcomes the problem of stretching up if the ladder is set below the window, and reaching inwards if set above.
I have a tutorial in the use of these ladders, based on my 40+plus years running up and down them! If anyone would like a copy, email me via my website below.
Ian