I can attest to what Johnr has said. Having worked for a Toyota dealer that was also a large Advance sweeper/scrubber dealer.
I am going to say that our rental, and this covered 2 states, was only about 2% of units purchased.
Also as Johnr mentioned these things eat parts. Let me put it this way, which happens to be a true story, one of our customers tore the front drive unit off a scrubber and when I asked why they continued to have this person operate this scrubber they said that "because he could not operate anything else with out destroying it." They figure how can some one do any damage on something that is traveling less than 3mph.
As far as rental goes they can be a nightmare. You would need to make sure that whoever you are renting it to is actually using it for what they said. Had many a unit come back that was totally destroyed because they used it to pick up concrete dust and then let it sit for a day or two.