ck it first!
I would've told you no worries about using a used one, until someone showed me mine wasnt working.... The person selling it may not know if its really working either - just because it turns on doesnt mean much.
make sure you test it before you buy it. like i said, mine quit receiving last yr, but it turned on & looked like it was working. no physical signs of damage either.
this is how i was told to test ( i believe its in another post here): separate beacons out of range, then turn one to search & start moving closer to each other. note the distance when it picks up the signal (mine didnt pick up until within 10'). If you do it the other way (start close & walk away), i was told it can hold the signal it locked in when close & falsely appear to be working.
hope that helps someone. if the beacon works, used is great!