When to Monetize Facebook Page?

I own a popular local printed magazine and we started a Facebook Fan Page. We started a Facebook page before the Fan Pages came along, so we have over 4k "Friends", and then 2 years ago we started our Fan Page and up until last week when I started working on it we only had 1000 likes. (We are doing away with our "Friend" page because it is causing too much confusion) Now a week in of actually working on building our fan base we are at 1,500. Our magazine is based demographic that could extend way beyond local, I even have had people want me to take it state-wide, but logistics of that are long. But with Facebook we could have a national fan base.

I imagine it takes much more than 1500 fans to start monetizing your Facebook page, but what are the general tiers of monetization?

10k fans = what approximate daily, monthly, annual revenue (generally speaking)?
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30k """"
100k """"
200k """"


Thanks for any help and guidance. I will probably be hanging out here regularly!