Just start looking around online, see what 15k can get you so you can get a reasonable expectation for the basics like year/mileage/fuel use/size, etc. Then figure out what factors are more important to you, would you rather have something bigger to transport/carry something, something with good fuel economy, something more modern in design, something with less wear, etc
If you go buying from a dealer, prices will probably be a bit higher, but your chances of getting screwed on the sale go way down and they'd be much more trustworthy (as much as used car salesmen can be). Finding an individual seller will be cheaper because there's no middle man, but it's harder to be sure what you're getting.
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ONLY FIVE CAN LADDER.
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