How long is the process to expunge a misdemeanor case from 21 years ago? And how much would this cost?It was for possession of alcohol under the age

If you are eligible for a sealing or an expungement the time fram is usually from 6 months to a year to complete it.  This is mainly due to the delay while the Florida Department of Law Enforcement does a record check to issue a certificate of eligibility. They have  a large  backlog.  The application process and the motion and court process does not take a long time. To be eligible you have to have not been convicted on your charge and have no other convictions on any other charges.  No convictions means either it was dismissed or you received what is called a withholding of adjudication.  Depending on the jurisdiction even if you were adjudicated guilty and that is your only offense it may be possible to put you in a position to become elilgible for a sealing.  You would have to consult with a criminal defense attorney in the county where the charge occurred.