I have a soft heart when it comes to animals (I would say most of us do) and I once was in this situation...
I had a lovely flock of 8-layers, I adored them, typical chicken owner.
It was nice day when my dad brought home 2 "rescue" chickens, the lady rehoming them to dad had rescued them and made sure they were healthy.... I put them in the coop and everything fine till one day a couple months later...
I went out to the coop to check my chickens only to notice one of the "rescue birds" had her legs and wings sprawled out.... I assumed marek's. I was shocked.... We separated her and she passed a couple days later.
I kept her flock she was with for 3-more years and when they stopped laying we did the responsible thing to cull them on instead of passing them on (their was a rescue by us).
Already, first "rescues" I had taken in caused issues.... I had to change what I was doing!
It came time where we needed a healthy closed flock as we were starting a farm....
I knew I couldn't do the find chickens on FB/CL this time.... So came ordering a specific few birds and hatching our own.... This was our best chance at keeping a closed flock.
I was then faced with having more roosters than I needed.... I tried selling/rehoming every last one.... All I got was people asking if They could be used for meat.... NO!
Well then came the answer "why not?"
To tell you the truth I didn't have a good answer! But I still proceeded to think of one, a silly one!
Me- "because they need a good a life"
The buyer than proceeded to tell me had a good life and it would better to butcher than give them to someone who might not take care of them properly, cock fighting homes were an issue where I lived, etc.... It made perfect sense!
I then started butchering myself and now take huge pride in raising a bird I hatched, fed, loved, and cared for knowing I am not supporting those nasty commercial farms in anyway!
I was in that spot and even if I was able to take in "rescue" chickens I wouldn't do it.... I still have a hard time trusting myself taking in normal BYC's.
As some of you know I have my uncles flock of chickens, that are dealing with leg mites, worms, lice, etc.... I have butchered all sick ones, and won't be keeping any but I will Find homes for a few with letting new owners know everything they have gone, and illnesses I had in the flock before hand.
I would encourage people to do your research, Be prepared for illnesses to show up.
And I would Highly suggest you don't buy any chickens from people that won't tell you illnesses the chickens have had before, age, where they got them from, etc.... I know it may sound like a lot but this could be life or death for your whole flock sometimes.
A lot of people where I use to live would scoop up chickens from where ever and get them "looking" healthy then sell them for a buck.... So that is why I say ask lots of questions!