$10 · Leghorn chicks

I have Purebred Leghorn birds from Reliable Poultry in the US. These are production birds (not show birds). The pullets started laying at 4 months & have laid all winter. I am collecting eggs for the incubator to check fertility & will sell chicks from only the one hatching. I believe we can sex them or at least fairly soon after hatching?????? (Someone might know better than I as this is my first year with them). They have been healthy all winter & laid consistently.