I used to do that. Those cheap
pressure washer pump don't last if you use them often. I bought the best one Home Depot had and I made some great cash with it. I had to reinvest into ladder racks, ladders, extension wands, extra hoses and other things you don't realize you will need.When it went down I was screwed, so I eventually had two. Then I hired a helper. The money was pretty good, but the work can be hard to get because everybody does it. Overall, there's no money in it unless perhaps you're also a painter.