I would ask what breeds they are using for their cross. I have read about situations on these boards where people posted pictures of their "sex link" chicks and asked why half of them looked like roosters with "female" coloration. Clearly, the person they bought from had purchased straight-run sex links and then bred them to each other thinking the resulting chicks would be sex links and advertised them as such. It doesn't work that way. So, simply asking that question will let you know whether your breeder is a real breeder or someone hatching their backyard eggs trying to make a few bucks.