I didn't get into my first ballet class until high-school (although I studied ballet on my own before that), but since then I've known many ballet guys who started ballet for fun and exercies after their 20's, 30's, and 40's.  There's one guy who posts messages who said he started in his 50's.  (I assume you know that at 30 your chances of becoming a professional are nil, but you could still perform in local recitals if that's a goal.)

Hindering?  Everybody in any ballet class will be a different levels, and each will work the class for their own needs.  I take classes from beginning level to intermediate/advanced levels, and I don't hinder the classes and they don't hinder me.  The teacher will not stop the class or slow it down because of any one student.

I say go for it!  balletboy

P.S. If you're seriously into ballet, try the other parsimony forums.  You can get to them through links in the Male Ballet site, forum26541.  This forum27099 has some strange stuff on it at times (well, most times)

Also there's balletalert.com and danceart.com for message boards.  There are lots of adult students on those boards (along with many more kids!)