Well EggSighted4Life sell the eggs came as a second idea for the family. We got the chickens in the first place because the eggs in the grocery stores were so disgusting we could not eat them. So my dad did some research into good egg laying chickens and found the red sexlinks. Well little did we know just how good of a layer they are or the fact (or at least for our chickens) that after 2 years of laying they start getting sick and pass on fast. We tried to sell of the excess eggs to people that my sister and dad worked with. I never personal got involved in that part so I'm not sure if we made enough to cover the chickens cost or at the very least their feed.
If you're going to get involved in heritage breeds, you've a fair amount of work ahead of you.
Culling birds doesn't always mean killing.
If you're raising heritage birds, you want the gene pool as hardy as possible, but you'll always have that "one" that's special, that's fine, especially if she's laying, as long as you don't breed her.
Then there's the ones that you need to grow out some to make a decision, especially if you're evaluating cockerels as replacements.
Then, there are the ones that aren't quite SOP, but nonetheless really nice good birds. The eggs from these birds sell just as well. You just cannot sell their eggs as hatching eggs
All of these can often be sold as "pet" quality as opposed to "show" or "breeder" quality.