I just researched greatly before buying as I have a large brick paved area and walls etc to clean. You need a gas pressure washer that is 2,900 - 3,300 psi range for sure. All pressure washers come with varying nozzles depending on what you are cleaning, so not to damage areas like fencing as opposed to stonework. The round surface cleaner is a must addition for large areas. Plenty of video 'experts' to see on YouTube.
The Best Pressure Washing Videos of 2018 - YouTube