hmm, possibly an aunt or uncle, or even your grandparents? they may be an alternative if you don't want to get stuck back at home.

and to answer your question, you can't get emancipated once you're over the age of 18, since that's the age that you legally become an adult. once you're 18, you have all the responsiblities of an adult, meaning that your parents aren't required to care for you, etc., etc., etc.