The cars on offer are typically the Long Range versions from 2017 or 2018 with prices starting above $40,000.
Tesla is selling the used Model 3 with a warranty similar to Model S/Model X:
"Every used Tesla vehicle has passed a 70‑point inspection and comes with either a 4‑year or 50,000 mile warranty or a 2‑year, up to 100,000 mile warranty"
Those interested in a used Tesla need to consider whether it's worth to go with the particular car compared to both - new (even lower-trim version) or used sold directly by owners.
The other thing is that it seems that Tesla is selling customers cars, not waiting on the potential availability of the full-self driving feature. Earlier Tesla decided to lease Model 3, but without an option to purchase at lease end, expecting that in a few years the cars maybe will get a 2nd life as robo taxis.