When I wash brick it is new masonry. I clean off the mortar smears. I do use a lift but most of what I do is no more then 30 feet high. I do get 45 cents a sq. ft. but I tell them that the lift and acid is extra. If you are 100 feet in the air are you aware of how heavy that hose will be? You will have to have it tied off really good to the lift. If it ever shakes lose it will rip the wand right out of your hand. Cleaning off mortar smears is much more time consuming then just cleaning dirt or mold off of a wall. There is no way someone would pay me 45 cents a sq. ft. to wash dirt or mold off of a wall. I can clean up mortared smeared walls at about 250 - 300 sq. ft. an hour depending on how bad it is. I also have to scrape the wall for large mortar tags. Every brick wall is different. The type of brick, the skill of the masons, type of mortar used, how long since it has been laid, did they lay any of it in the rain, etc. Let me know if it is mortar you are cleaning or just dirt. If it is brick that has been there for a long time you can use some good pressure on it because the joints should be good and hard. This doesn't apply to sand faced brick though. With too much pressure you can discolor the brick and take off the sand finish. Like I said if it is just dirt or mold you probably won't get 45 cents a sq. ft. but you should get more then an average brick wall on the ground. The risk of being up 100 feet is where hazard pay kicks in. If I was to wash mortar smears that high I would probably charge up around 65 to 70 cents a sq. ft. What kind of lift will you be on?