I've got some Leghorns that I'm raising right now to sell as started pullets. I'm not keeping any kinds of records on their costs since I'm just doing it for fun this time around -- if the market is good that might change how I do things next time. I plan on selling them for $15 each, starting when they hit 16 weeks. I've already told the guys at the co-op, so whenever someone asks them where to get started pullets they'll be given my number. In another month or so I'll start putting signs up wherever I can.
You might want to consider the time of year that you're going to raise them so that you're not trying to sell them at the same time that everyone with chickens has pullets coming into lay. I got my chicks in January with the hope of being one of the first on the block, so to speak. However, it might be even better to time it so you have them coming into lay right around the beginning of the year so that people who sell eggs will see your pullets as a leg up on their business over the alternative of waiting till spring to replenish their flock. Also, since a lot of layers aren't laying in the winter, it could make folks think about investing in some pullets that will start laying before the others get into production. I can't tell you how many people have asked about the winter production of my flock -- and how I'm able to be selling fresh eggs this early in the year.