At the auction site where I sometimes take birds, most sellers don't stick around, they cage their birds and leave. Not a good selling point!
I write brief descriptions on each cage, and stay to talk to possible buyers, because i do want the birds to work out for whoever takes them home.
According to state regs, all those cages are disinfected each week between sales. NEVER does that happen there! Ample reason to not bring birds home from that sale, IMO. My birds arrive fine, unlike so many, but ??? about others.
They also sell some pigs, goats, calves, and sometimes mini horses. Same problem; no way to know what, if any, diseases might come home with any of them.
I think that swap meets, as
@centrarchid describes, might be a bit safer. And, BTW, I don't recall seeing nice game type chickens at this auction, ever.
Mary