Can't contact garage tenant (but he's still paying)

[Clark Kirkpatrick]

Strange situation: I bought a duplex with a garage, and the garage tenant has been there for 15 years +. He hasn't been to or opened the garage in at least a decade, and he still sends a money order to the previous owner each month like clockwork.

We need to get him to start sending the check to my PM company, and the only contact info we have for him is his return address on the envelope he sends his payments in. We've sent him letters but he won't change where he sends the payment.

Any tricks to tracking him down in some way so that we can get in contact with him and get the checks coming to the correct address?