#1: Live in da USA. #2: Have patience. #3: Have content. No, not the ugly for YPM ads kind of site!!! #4: Have patince. #5: Update site. #6: Oh, did I say, 'Have patince.'??!!! Don't plan on geting the invite any time soon!!!!!
If you are asking in terms of minimum unique visitors or page impressions. Then they haven't explicitly mentioned it.You can apply if you are in USA.