I want to be 1 of those music video models/dancers in rap/hip hop videos and I know that you got to audition for them but where? How do I found out? Is it in newyork or something? And do you just go there or do you got to have a manager/agent & a portfolio or what? Because I really want to do this but how do I break into it?

Answers4Dancers - Music Video Auditions

Also, the following search may be of help: video auditions dancers - Google Search

And basically there are auditions held in almost every state almost every week. You will have to review dozens of music and dance publications.

Lacasting.com and Nowcasting.com have auditions for music videos, and film, and television, etc...
You'll need to get headshots, to get auditions, so you can sell yourself. On Lacasting.com they have a long list of photographers.
Pick out headshots, add them to both websites, and submit for auditions. They will call if they are interested.
Good luck!

I wouldn't do that if I were you because I saw a show all about the women who are in those videos and they are degraded from day one.I know you probably won't listen to me but just some advice

Not all videos are degrading! I did see the show that maleese805 is talking about, but those were for rap videos. And they were rapping about sex! Of course that's going to be degrading to women, but not all videos are like that... So I would go for it!