I've been reading a lot on here, with much of the advice geared toward the 4.0gpm units being a minimum. However, I'm not planning on using the unit in the same fashion most of you do. I have several rental properties I want to wash and keep clean, plus I add a property or two every year. In all of them, I'd do the following: clean the garage floor, clean the driveway, spray down the siding, etc. Plus, I'd do that to my two houses -- main and vacation. Finally, I have several vehicles I'd like to keep clean. I've found a 3.5gpm/3800 psi unit that's in the price range I like. It won't be running 40 or even 20 hours per week -- more like approximately 15 hours per month. I don't think the consumer units can handle that but I don't want to spend the $1500 for a good pro unit. I understand some of the pressure adjustment is made with the tips, but can this 3800 psi unit, with the right tip, wash a car without damaging the paint and tires? Thanks for the input.