When people are recommending hardware cloth:
1/2" holes are small enough to keep out most predators.
1/4" holes are needed if you want to keep mice out.
1/4" hardware cloth is usually made from thinner (weaker) wires than 1/2" hardware cloth. So the 1/2" is often a better choice, because it is...
I agree with other posters that it is good to do research, then build the coop, then get the chickens. You can brood young chicks right in the coop. Remember to check for zoning restrictions and HOA rules. Some places say no chickens and some places let you do whatever you want, but there are...