Some breeds may begin to lay around 20 to 25 weeks, most take a little longer, 5-6 months, some take more. Some are seasonal layers. You really need to find out about the breeds you have. If they're mutts, it's anybody's guess. They're not trains. They don't run on schedule. They'll mature and lay eggs at their own individual rate. Some early, some late, just like everything else matures, including people.