Thanks for taking the time to respond.OP, it is important to take into consideration what trafficat said about being fired from Uber or Lyft. Do a search in this forum on "deactivation". This is not a gig good for anything other than SUPPLEMENTAL income. Neither Uber or Lyft are profitable concerns, so in addition to the random false accusation it is unclear how long rideshare services can continue in their current forms.
With the labor shortage being what it is there are other jobs paying more and having better job security.
Furthermore, I would not purchase a car up front if you have never done rideshare before. What if it doesn't work out? See about renting at first.
Finally, if you chose to plunge anyway, a Prius is an ideal rideshare vehicle. As to whether the Prius you are looking at is worth $15K, we have no way of knowing. Depends on the condition of the car and the average sale price in your area.
Good luck. Don't hate me for telling you the truth.