In Rent, how old are the characters?

How old are the characters in Rent? Mimi said in one song she was 19, but she looked a little old in the movie. And Rodger looked like he was at least 25-30, and that would be a little old for Mimi. So would Rodger be 20ish? He doesn't look like it. And Collins seems really old, same with Benny (I fell in love with Benny's voice in the movie, didn't you?) Nayway, any ideas?