Before you even contemplate getting any chickens, please ask yourself: "How will I kill one or even
can I kill one if it needs to be put out of it's misery? Are these strictly pets and not to be used for food? If not, then is the rest of the family on board with eating spent layer hens? If pets, do you intend to keep them even after they have stopped laying? If not, how will you then get rid of them?"
These are more important questions than buying hens or chicks. These animals are not like cats or dogs and most vets will not even treat chickens, so you really need to have an idea what you will do in case _____________ should happen to your chickens. Fill in the blank with sickness unto death, injury, etc.
Every predator's favorite food is chicken...do you have a plan to protect your potential flock from predators?
Finally, have you studied up on chickens at all, as a previous poster suggested? Symptoms of typical poultry diseases, flock management and feeding, available medicines in your area for treatment, or even how you will treat them naturally if you choose to do so.
All of these things suggested are real concerns with raising chickens and should be truly studied before getting your flock. You will be glad you have a plan in place when you have to face these realities later.
As for hens vs. chicks? I've bought a whole flock of grown layers before with great success and was entirely pleased with their health, breed characteristics and egg laying abilities. One just has to gauge the living conditions, husbandry methods and general appearance of the flock...then take a deep breath and take a chance. There are no guarantees when it comes to chickens, be it chicks or hens.
Oh...and have fun!!!