The short answer to this, is that you can't run a competition without speaking to an Admin first. Here it is, explained in the rules:

3.9 Contests, Sweepstakes and Requests for donations is prohibited without Admin approval.
But it might also be useful to know a bit more about what we mean by that.

Essentially, we want to keep tabs on any contest so that we can make sure our BHW members are getting what they are promised and are being treated fairly. In order to do that, we ask that you provide us with the prize and we pick the winner from a publicly submitted pool. That way, the contest can be impartial and transparent.

We charge $250 per competition.