There is really no difference between fertilized eggs and non-fertilized when it comes to eating them. They look and taste the same.
The roosters will mate with the hens year round. The hens remain fertile up to 3 weeks after the last mating as they store up the sperm.
When figuring out how many hens, figure on an average of 5 eggs per week per hen, for most of the non-production breeds that are still good layers. That will vary greatly depending on the breed of hen and time of year, age of the hen, and also individual differences but that's a good round number for a young flock.
Certain breeds are better layers than others. What else are you looking for and we can help you decide what breeds might be best for you.
Some questions to think about...
Are you looking for layers that also are good meat birds? Do you live in a very cold climate (need more cold hearty birds). Are you looking for pure egg production chickens, or do you want more of a colorful variety for your back yard. Is a 'personable' or sweet breed of chicken important to you (ie- pets with benefits) or is that not as important?
Do you WANT or NEED a rooster? If you just want eggs, you don't need a rooster and roos are generally more agressive than the girls. Also they do crow so if you have neighbors you may choose not to have a roo for neighborhood peace and quiet. Obviously, if you want to hatch out chicks, you'll need a rooster.