Be very careful buying used monitors.
Make sure you can listen to them at a variety of volumes, that they're closely level-matched and that they're in good cosmetic shape.
There ARE good used monitors out there to be had, but there are an equal number of 'wash 'em down good and sell them to a sucker' types who you need to beware of.
The one thing you more or less need to resign yourself to is that your first choice monitor may or may not be available at the time you've decided to buy.
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