I would either have my attorney look at it OR have the seller pay for title insurance in your son's name OR both. If there is a lien that has not been taken care of in the transfer, the insurance will look very cheap! 

You can do your own lien search by checking with your county recorder (my county has their records online).  You will be able to see each lien that has been filed and you should find a matching RELEASE at a later date.  If you don't find the matching release, you can contact the lien holder to see if money is due.