5 or 6 chickens should give you about 3 to 5 eggs a day. Chances are you will want to buy the chicks locally rather than have them shipped, unless you decide on some exotic breed. The advantage of that is that the birds have recovered from shipping stress, and you can hand pick the larger and stronger looking ones. Check around for feed stores or farm supply stores in your area; you should be able to find out who will have baby chicks. Sometimes they will let you order what breed you want, and sometimes you will have to choose from what they decide to order. You should be able to find out what they got this spring; probably won't be that different. And don't expect the employees to be knowledgeable about chickens; often, they are not.
You could also look into buying older birds such as started pullets, especially if there is a good breeder near you, who will also probably sell chicks at least part of the year. You should be able to find out who is close by on BYC, if there is anyone. If you can find one, that would be an ideal source, as the quality of their birds is better than hatchery birds, which is what the feed stores will sell. Most of us have hatchery birds, though, including me; nothing wrong with that.
Do check out that My Pet Chicken breed selector. And here is a link that gives a lot of info on the various breeds, including cold hardiness:
http://www.ithaca.edu/staff/jhenderson/chooks/chooks.html
Leghorns are the classic egg chicken but they are NOT docile, they are usually flighty, run from people, and do not like to be handled. And there will be times you will need to handle them. My preference is for the dual purpose heavy breeds, such as Orpington, Australorp, New Hampshire Reds, Dominiques, and Barred Rocks; the first two are particularly docile, and all are good layers (meaning about 6 eggs per week rather than one or two.) There are breeds like Cochins which tend to be docile but don't lay so well, and also tend to go broody. You will want to avoid the more broody breeds if this is only for eggs, as broodiness stops them from laying and is often rough on their health. On the other hand, a good broody is a great way to incubate eggs and raise more chicks, from your flock or elsewhere.
Good luck, and have fun!