I know that many have repeated the "ex-rental car" comment over the years, BUT there are some pluses to them. Of course, it can depend upon the rental car/lease company that had them, I suspect. National chains vs. local/regional companies, for example.
One plus is that they will not be "stripped", but nicely equipped. Generally not leather, but cloth/vinyl. Generally the upgrade stereo, but probably not all the way to HD radio. And you know that they should be getting regular maintenance.
But one of the best things is that as they had that car in their fleet, it CAN be a sign that the car is pretty reliable and trouble-free. A "broke car" makes them NO money, so getting the model and equipment "right" keeps everybody happy. But they'll also usually "turn them" at less than 20K miles, which can limit their exposure to potential "ill use".
In prior times, if they got "run hard" too much, it would usually impact their ultimate reliability/longevity. Not quite that way with the newer stuff. The ECM will not let the driver so some things which would have caused earlier powertrains to fail, for example.
I believe that under the OEM agreements, when the cars come back in, they have to meet certain standards. If not, they are repaired to make them compliant. Then they usually go to the OEM dealer auctions, rather than normal used car auctions. If they get a significant wreck, then they probably get fixed and turned, I suspect.
If the car had always been in private use, then any dealer can pull up the warranty repair records for that VIN. Which can also serve to verify the mileage. hehe Plus any maintenance done on a "full maintenance" program, extended warranty package, or otherwise. Yes, the rental car might have seen some more intense use, but at least you know it been serviced regularly.
Anyway, do due diligence on any purchase.
CBODY67