Think what you want it for
Yes you want it for home use but when you have a good one you find other uses for them!! Like cleaning the brickwork, garage doors, the patio, the block-paving drive... the list goes on. It's amazing what it does to a dirty patio - no need to bother with any cleaning fluids - just blast away with water. And while you're at it ...your boots, window, window frames, lawnmower. We should have a competition really!!!!
Buy the best you can afford - the cheap little Karchers have plastic moving bits and wear out if used a lot. Just go into your local specialist shop and see the piles of them awaiting service. The better units have metal bits throughout including the nozzle on the gun thing.
Having a drum which winds on the 15 metres or so of hose is useful too.
Mine's a Karcher 620, others here have the 720. Do a search.