How much to charge for washing down walls?

Depends on how large the walls are....in a standard sized apartment, i would say $5 per wall.How much to charge for washing down walls?
Charge by the hour and figure out how many hours it takes to do the job. I used to do this with apartment cleaning and it was necessary sometimes because of smokers. You basically had to mop the yellow gunk off the walls and ceiling before they could repaint. Since its unskilled labor, you can only get about $10/hr, if that. A small apartment would be about $50.