Be very careful when you are buying from unknown people. I cannot say this enough. There are people out there that have no issue selling diseased birds/chicks, Marek's, MG, MS, etc. Some going so far as to dope their birds up on antibiotics prior to sale so they may "look" healthy. The best advice I can give is to do your research on poultry disease as well as the person selling. Ask at least 10 people about a particular breeder. There are pages on Facebook, 'Good Eggs, Bad Eggs, Reviews About Poultry Buyers and Sellers' and many more that you can search a person or farm name. Quarantine the birds. Many poultry diseases will surface (show signs) when a bird is stressed; a new home, new people, new environment. Biosecurity is the key.