>How big of a risk do you think used equipment is?
If it didn't have AFB, none. If it did, huge.
But how do you know? I buy it all the time and just use it, but I try to assess the seller and if they are honest about the problems and I look for scale in the brood combs (signs of AFB a long time ago).
Is it wise of me to use it? I don't know, but I haven't had any problems.
Some states have laws about bees on combs, but most just require an inspection certificate from the state they came from.