The big thing is the cost of feed. You need to know about how much a hen of the sort you'd like, eats in a month; and you need to know how much a bag of feed costs in your area.
I live in a non-grain-growing part of the country, and a 50 lb. sack of regular feed costs $15 CDN, and the organic feed costs $19 CDN. I can't tell you yet how much my 13 birds eat in the course of a year, as I've only had them for a few weeks, and they're still growing! But I can tell you that, even though I live on a modest income and feed prices are high, I feel that I can afford to keep laying hens, and trust I'll be able to break even if I sell the eggs I can't eat (urp!). The local market will bear $4 a dozen for local, large, free-range/organic eggs. Sure, people can pick up factory eggs at the distant, special-trip supermarket for $2.79/dozen, or $3/dozen at the local general store. But there's a general feel-good factor about supporting happy chickens and local producers, especially among the vacation cottagers. And even if this hobby/chicken 101 course ends up costing a little, rather than earning a little, I'm enjoying it thoroughly, for the same reasons that many have eloquently stated!
Be ingenious and thrifty with the coop, shop smart with the feed, put the chickens' needs first to avoid vet bills, and I am sure you will find yourself an affordable, practical hobby.
Edited to add: 13 chickens are cheaper to keep than my two dogs, who don't lay eggs, and I certainly don't want to eat them! :O Does that help answer your question?