How long before Google AdSense will be allowed within a forum?

[Rumpelstiltskin]

I just wondered about a time frame for this because i want to create a group of forums that i can place AdSense in to the actual forum. If it is not going to be too long i can wait but if it will be months i will have to find another forum that allows it. Thanks. Also will this be available to the free forum users?