With selling eggs, you have to watch where you sell them an the ordinance. In NJ, permits are involved if you actually want to sell to stores and distribute. They really aren't hard to get, but the state will come and check any food production facilities to see if the animals are healthy, the animals are well kept, and the building is sanitary. Their standards are low, but they do take food safety into account to prevent disease outbreaks. The easiest way to sell is at local farmers markets. People love fresh eggs. I've considered it, but there are quite a few people who sell eggs there already. One person rips people off particularly well because her olive eggers lay a deep green colored egg, and people actually pay more because it is green. Can't make it up.
As for breeds - you need a production hen if you want to sell. This is sex links, golden buffs, golden comets, and any other cross. If you are in a warm climate, you can do leghorns, as they are prolific layers of white eggs. They're also rather efficient when it comes to feed. It is good that you are crossing your own chicks, however it would have been just as easy to buy the red sex link hens and go from there. Production birds can be tricky though. They develop many more health problems than a heritage chicken because they have been bred to produce. Egg peronitis happens, and sometimes they just drop dead. A lot of egg producers or chicken owners who want a lot of eggs opt to replenish, or swap out their flock every two years or so. Hybrids will not lay as long as heritage. To combat this, you can raise rhode island reds or australorps, as they are extremely reliable heritage producers, however even their production is slightly less than that of a hybrid bird. ***Somebody above suggested cuckoo marans, and while they are great birds, they are not as efficient as hybrids either. Their dark brown eggs are pretty cool though.
Lastly, you'll need to find a feed supplier and buy bulk. Layers can eat a lot of feed, and you'll probably do best feeding them a layer mash and then additional nutrients and scratch. If the birds are free ranging, be sure to offer extra calcium like oyster shell because they probably won't find much out in the field. Layer mash by me runs about $11 for a 50 lb sack, and the quality is pretty good (much cheaper than $18 Purina), and when fed with additional nutrients, it gets the job done well. Since you'll be buying bulk, you should be able to get a good deal from somewhere.
