Rest assured, despite what certain animal rights groups claim, the vast majority of research animals are purpose bred. While there certainly are some corrupt animal dealers out here, cosmetic and product testers are not interested in chickens, military testing applications for chickens are likely to be limited, and pure research testing uses chickens mostly for genetic, ag, and social/behavioral work and is generally interested in obtaining genetically similar birds free of disease (so not backyard flock birds). Ie. a large pigeon genetic study used mostly feathers provided by breeders from birds with known lineages...not Craigslist pigeons!
Much more common on classified sites are money scammers, people scoping out homes for theft or other reasons, and people interested in free or cheap animals for reasons such as snake food. For the latter, simply setting an asking price that is above prices for shelter dogs and cats, feeder rats, pet store rabbits, etc. solves many a problem. When Class B dealers go bad, they go bad for cheap, and usually in the area of cats and dogs rather than chickens.
