I am looking at getting into home exterior cleaning next year. I am going to buy a commercial grade pressure washer around 3300 psi with chemical injector. If I decide to start getting into roofs later on will that work? I know I do not need a bunch of pressure for siding and roofs, but I want the power for concrete and other hard surfaces. I can always turn the pressure down. Also, any suggestions on cleaning chemicals for different surfaces would be great.