@USVeteran, if you're buying used, Ritchie Bros. is a solid place to start, just make sure to check the hydraulics, tires ,and overall condition, and don't skip the inspection reports.
Take a look at the pins and bushings, too. If there's a lot of play in the arms or bucket, that can get expensive fast. Same with tires or tracks-they're easy to overlook but not cheap to replace.