About spoiler permission

I've been searching for a forum site and then I found this . "To view spoiler content you need 30 post and 30 days registered here"
How can this be done? Can anyone help me? Thanks in advance.I mean I have my xenforo forum.All I want to do is only registered member or have a rank for example forum guru or established member only can view spoiler content. Can you help me with this please.All I want for this is to avoid my post to leecher.