If your wanting eggs for selling purposes a higher number of girls would be safer.Fully depends on the breed! Reliable breeds such as Barred Rocks, lay quite frequently and you could probably get 25 eggs a day with 25-30 of them. Silkies, On the other hand don’t lay as frequently, because they tend to go broody causing a break in their egg laying once they have a clutch.
(I’m being very discreet trying to pick out some breeds maybe you have heard of, there are lots of high production and low production birds out there! Tons!)