I have had my Ninja for a few years now. I mostly use the hard surface acid. Althouh more expensive it cleans much better. I charge .50 cents per sq ft plus extra for moving furniture.
Also have been cleaning VCT for a few years. My largest job is 23,000 sq ft that we clean every 6 months. It’s alot of work but takes us less time each time. The money is pretty good.