All of my silkies have started laying around the 24 week mark, some sooner and some later. Most of my silkies lay everyday that they are not going broody and hatching out chicks. I even have some that lay straight threw the winter, but we live in Georgia so our winter is mild. Silkies lay really well when they are laying, but they go broody a lot so I hope you want lots of chicks.
Hope this helps.
Edited...you could research in the "Egg Laying" section on BYC.