Is this a question?
If you're asking how many you are ALLOWED by law, code or restrictions, you'll have to check with the governing body in your locale.
If you want to know the practical limit you can keep up with, well... Who knows?
I'll offer this and let you chew on it. Back in the days of free ranged market rearing, 500 layers per acre was considered the MAXIMUM.
This was based on the sodded earths own ability to absorb the effects of the birds upon it. Anything less begins forcing you to add waste management schemes to your poultry keeping efforts.
If we do a little math....
[acre] 42544 sq ft / 500 = 87 sq ft per bird.
If you can provide AT LEAST this much fertile sod per bird*, and properly care for and protect them, well ... The sky is the limit.
* If you're asking how many I MYSELF CAN KEEP, I have allocated 1/10th of an acre for them. This means I will have no more than 48. Rounding down for safety, I set 40 as my practical limit.