Delivered for a hour the other day just too nice big ones! 
And found out i might get another 5 or 6 on the same street!
The window cleaner hurt his leg in december and not been back! 
i think you are being out of order by doing this work if hes really damaged his leg he may want to return WOULD YOU CLEEWINDOWS give the guy is work back ?
if you went about it the right way and got in contact with the guy to see if he was going to return before you started doing the work that would be better , you never no he minght not beable to return and he minght put other work your way , but dont just take it without finding out if he will return .
otherwise it minght come back to haunght you .
i would guarantee if it was my work and i ended up sick for a few months i wouldnt be a happy chap .