Answer:
First, you would not pay a company that says they can do this for you. Depending on the offense, you may need to hire a lawyer to help you through the civil process.
Youthful "indiscretions," or other incidents that occurred quite some time ago, without being repeated, are often reasonable candidates. If the offense caused you to be listed on a list of sexual offenders, or other list, the chance of having your name removed from the list is unlikely. In any case, if you are applying for a job, you may still need to list the conviction as being expunged, since a background search is likely to find a citation of the offense.