I don't have my green card yet and i'm out-of-status right now since my k1 visa is already expired. but I plan of going to school some time on Spring. Would this be a problem?

Depends on the school, really. I know a couple guys on B-2 visas that have been expired for about 15 years, and they go to school with no issues. You could have an issue with instate resident rates and be charged international rates, but Florida gives derivative state resident status - if you get married and your spouse is a Florida resident and this can be proven, you are automatically a Florida resident and the 12-month residence requirement is waived.

Have you filed for AOS already or are you completely out of status? That's the first thing because if you're out of status without even an NOA1, then that's a whole different issue.

You should also call the school to find out what kind of documents you will need to register. My husband was asked for both, his green card and SS #, the documents also gave him in state fees.

Diana