People advising CPO above all the other options are definitely spot on  *if* you are buying a higher cost car and want the extra assurance of a warranty.  I recently bought a new car for my wife, a 2015 with 18K miles and the remainder of the 50K B2B warranty, plus an extra 5 years 100,000 mile powertrain warranty after that.  The original sticker cost of the car was 51K, my price (after some extended negotiation) was 29K and change.  If you're buying a CPO car that was less expensive to begin with, then the savings can be considerably less.

 

If you are looking for something new under 30K, I'd say consider Edmunds or Autobytel for a good internet price rather than paying a fee to have someone locate a car for you.

---