I'm buying a mobile home and I want to know if I put my son on the title with me but he has a judgment against him does that put me in danger with own

Yes.  If you put your son "on title" you are granting him an interest in the mobile home,which his creditors can use to satisfy his debts.  There are ways to structure the transaction to significantly reduce your risk, however, such as conveying a life estate to yourself with the residuary estate to your son.  Without the legal jargon, that means you would have the right to live in the home for the rest of your life and your son would get it when you die.  Of course, his creditors would be able to come after it at that time.  You may want to consult a local real estate attorney.