Recently totaled a rental car. I paid $15,000 out of the total$18,000 does the car now belong to me?

The car rental company wanted the car paid for, and did not want to wait for my insurance to issue the check. I want to find out if the car now belongs to me since I will be paying the total $18,000 for the car.

Ask the rental agency. If the car is a total loss and you are paying the total value, it makes sense that the vehicle should now belong to you. Even as scrap, it has a little value and that should be deducted if 18,000 was the true value of the vehicle when you rented it. I suspect this may become a "fine print" issue though.