How old does a rabbit have to be before it's ready as meat?

The longevity of a meat rabbits life is influenced by many things.

Factors such as having proper housing, living in clean conditions, having the appropriate amount of proper feed as well as having fresh water always available all affect lifespan. Other factors include how aggressively the rabbit was bred, how well the rabbits weight was managed (overweight rabbits don't live as long) and if the rabbit was kept free of temps that are too hot. Cold is OK, but too hot can be fatal.

In general, a meat rabbit that is bred on a production schedule can be bred regularly starting from 3 months of age right up through about 3 years of age. Some might breed a bit longer, some will stop a bit sooner, but 3 years is the average breeding life. The rabbit can physically survive for several years beyond being retired (they can reach 7-8 years old), but since you asked specifically about meat rabbits, I'm giving you info on the breeding life.

Bucks can breed longer than does and can continue to sire litters until about the age of 5. Again, they can be kept as pets for a few years beyond that, but that is the end of their breeding life.