Hi Hawkins,
Below is a cut and paste from advice I wrote a while ago to help begineers chose their first birds. It might not exactly address your question but I'm sure you can extract a few questions from it.
"I believe it’s always best to buy known healthy birds so visit a breeder and see his birds in situ and how they are being kept as this will be a good indication of their likely health. If the breeder is a hobbyist keeper who is selling off their excess home bred stock it might well be that the birds have not been vaccinated for any poultry diseases and you will have to decide on your attitude to buying such birds. Obviously knowing something about the breeder is very important and it's good if you can get a personal recommendation.
If the breeder is trading commercially you should expect to get a comprehensive coverage of vaccinations and some guarantee on returns if they prove to be unhealthy. Vaccinations you should expect are Marek’s Disease, Gumboro Disease, Infectious Bronchitis, Newcastle Disease (Fowl Pest) and Coccidiosis. Other diseases which you might ask about screening for are Lymphoid Leukosois and Chronic Respiratory Disease (often called Mycoplasma). For professional commercial breeders you should also ask about what testing they do on their stock for salmonella and whether they follow DEFRA approved schemes for poultry breeding. If they keep more than 50 chickens their flocks should be DEFRA registered. However as I said don't expect this level of coverage from the amateur enthusiast breeder but a commercial breeder should have a quality health regime simply to protect his stock and their business. Whether commercial breeder or enthusiast any stock offered for sale should have been wormed and be free from lice and other creepy crawlies.
Ask questions about the chickens, who and where they were bred, what experience they have had with the particular strain, are they for example good layers etc. Make sure he knows something about them and they haven’t just arrived that morning off the back of a truck. Check they are bright eyed, there is no sneezing or discharge from their eyes or nose, that their rears aren’t heavily soiled with droppings, that their legs are smooth and healthy looking with dark pink blood vessels (on lighter legs) and tight scales. Check they are true to type and don’t have any deformities or appear to limp, that they don’t have feathery legs which the type says should be clean (for pure breeds). If you are thinking of showing or breeding pure breeds you will need to be pretty fussy (and knowledgeable) about the markings and confirmation of the birds. Ask how they select and maintain their blood lines and, if they show, and how their birds have faired in showing classes. If you aren't fussy about showing then if they look attractive to you then you needn’t be too concerned.
Look at the breeders other stock; is it healthy looking and being kept in sanitary conditions with food and water? Don’t necessarily be put off if there are a few feathers missing as birds tightly confined in stock pens often can get a little pecked from their companions but there should not be excessive bald patches or open wounds. Young birds can sometimes be difficult to sex so if you are buying them as hens ask if they can be replaced or the cost refunded should they start to go cock-a-doogle-doo!
It is best that you get all your birds in one batch at the same time so they acclimatise together and this minimises the health risk and pecking order disputes and acceptance problems you would have introducing new birds to an established flock. If you do need to introduce new birds try to have at least a pair as a single bird will be badly bullied, also make sure they are of a similar level of maturity, don’t introduce young birds to older ones. Also it is better if you have a large run area so if there are disputes the newcomers have space to retreat to. In any case you will need some patience and it is essential quarantine new birds for about 3 weeks to check for any diseases which can show up after the stress of moving. It is best to go though slow stages of first siting the new birds in a run close to the established birds so they can see them and get acquainted. After a couple of weeks you can introduce the new birds into the house after the others have roosted. Chickens are docile in the dark so the established birds won’t bother them. However expect a few feathers to fly when you let them out in the morning. It is possible that the established birds will guard and keep the newcomers away from the food and water or the house so to counter this put several bowls of food and water in the run so they can’t guard them all. Having a larger run to do this is best. They will eventually be accepted and take their place in the pecking order.
When you get your new chickens home they should be placed inside the house and kept in until the next morning then released into a run so that they get accustomed to the house and therefore go back to roost at night. You may have to encourage them out of the house at first but they will soon become bolder. After a couple of days confined to the house and run they will be 'homed' and you can let them free-range and they will always come home at dusk."
HF