<prompt> Human: A little context. I drive a 03 trailblazer and get 18mpg driving 50 miles a day for work. At current gas prices I spend around 40 a week on gas.My sister is moving and wants to sell her 16 hyundai elantra, which gets about 36mpg. She offered to sell it for me at no cost expect to take on the payment. 300month with 5000 left to pay off.Ive never liked to have debt but in this case Im considering it. If I sell my car for 3500, generous but not unreasonable, and put that directly towards the car I would be able to pay off the car in 5 months. So after doing some napkin math I figured after 18 months I would have saved the amount I spent on the car in gas.Another thing is, and Im not sure about this, but I think my insurance premium would go down. Being an 18 yo male with a fun car Im paying 140month. Would the her car be cheaper with insurance?Somewhat related, my lease is up in January and Ill be moving back with my parents for a couple of months until I can find a new place, so I could possiably pay off the loan even faster.So I know this subreddit is big on cutting cost and thats why Im considering this, but is there any reason I should, or is this one a no brainer.Edit: Thanks for all the advise, Im hoping she gets the job and moves.  <response>: Also, if theres a lien against the car, youll have to carry full coverage insurance. Point being, you should get a quote so you have solid numbers. 