It depends on the individual hen, and the breed and age.
Sex-links lay 6-7 days a week for thier first year or two, then it slows.
Multi-purpose birds (Orpingtons, Easter eggers, barred rocks) lay 3-6 eggs a week thier first two years.
And it will fluctuate with the weather, light, season, ect.
earlybird x2. I have isa browns, barred rock and brown laced wyandots and I get about 2 eggs every 3 days from each of them. my isa browns are a year old and the others are 2 years old. They will slow down after they get older. yet, chickens may lay eggs for 5 years or more.
Your question has many, many answers. Every breed of chicken has different laying capabilities (as stated above by earlybird and chickie farmer), however conditions can also affect laying. Hybrids and sex links will lay the best, as they are specifically bred to do so. Australorps will also lay a ton of eggs for a heritage breed. If you add supplemental light, your birds will lay longer. You need to specify what bird you will be getting so that we can tell you how productive they will be.