I hold a mortgage for the house my son lives in. At 25 my son gets money for a trust that will pay the house off.

If you are holding a mortgage on the house that your son lives in, is the owner of the house someone other than your son? Clearly, you are not the owner because you would not hold a mortgage on property that you also own. If your son is the owner and he pays off the mortgage, then you would need to prepare and record a satisfaction of mortgage in the public records of the county where the property is located.  If a third party is the owner of the property, then that third party would need to agree to convey the property to your son in exchange for satisfaction of the mortgage. That seems like an unusual situation, so I hope your facts are that your son already owns the property and you merely need to release the lien of your mortgage after being paid off. The foregoing is specific to the law and procedure in Florida.  This response does not constitute legal advice as the facts presented are limited and unstated facts will likely impact your particular situation. This response is intended for general education only and does not create an attorney-client relationship. Please schedule a consultation with a local attorney for more specific and detailed answers to your legal issues.