Best approach evacuate difficult owner for foreclosed home

[Liz Murphy]

Am purchasing a single family home in NH.  Apparently the owner has been battling in court the mortgage company for years.  Likely to be a messy situation to evacuate this current owner of the property.  Is there a law firm or lawyer one can recommend understands NH law and what options I have to best evacuate this owner?  Am guessing cash for keys will not work in this situation - so looking for legal/law help to get him out.  Thanks for any advice!