[thegranderson]

Once you do some research on KBB and the like about what cars are reliable to buy used at that price point, I like Cargurus.com for actually finding the car.

They have a ton of inventory, can connect you directly with the dealer/seller (some are sold by owner), and they include the important aspects of a vehicle history search. This last part is critical at that price point, because you'll see things like flood-damaged cars, major collisions, etc. You may choose a car that has those things, but its better to be aware of it before you buy vs. finding out later. CarGurus also has a good metric of whether a car is a good deal, based on all similar cars being sold (and they have almost all the used car inventory in the US on their site).