It depends, are you offering this for walls or concrete drives? Is the surface any bit fragile? Would this be a 1 man job?
My guys usually get around $15 an hour for this type of job. I take 20 to 30%.
Charging 15-20/hour seems low to me. I started a small pressure washing business in my neighborhood when I was young. I just did decks. I would charge $50 for a small deck and $100 for a large deck. It usually only took an hour or 2 and I loved the money when I was that young!
I've been in construction since I turned 16. It's mainly been roofing. The cleveland roofing industry has been good to me. My bones are starting to ache though. I'm proud that these hands have helped build America and homes for it's people though.
The pricing totally depends on the scope of work, if the pressure washing applies to the entire exteriors, including the windows cleaned etc. Please refer to a couple of articles that have references made to the pressure washing technique, how to do it and the window cleaning job along with.
I agree with cleanway you have to look at the whole job.another thing you need to take into account is how much do you want the work?
I have had times when work was lean and slashed my rates by 50% just to keep going