No, there is no such rule in Bitcointalk contests, all winnings are instantly available for cashing out with just 1x wager requirement. Same goes for entry, only 1x wager is required and you can do it anytime on any game during that week.
I understand what you are trying to say but what I actually meant is that those poker events sometimes require that you must have staked with that particular casino at least a certain amount (which they usually specify on the poker announcement thread) before you can participate in the event. If some of yours is different ( meaning I can play and later go on to stake with the casino) then I actually don't mind giving it a try. On a honest note poker is getting more popular on the forum.