Owner's Son Doesn't Want to Sell the House

[Kevin Glover]

I sent out a direct mail campaign and got a call from a motivated seller a few days later. She lives in Chicago and owns a house in Phoenix free and clear. She is ill and wants to sell the house to relieve herself of the burden and provide some cash for her son and grandson. The problem is that her son is also on the deed and does not want to sell the house. She told me that he did not sign any paperwork during closing when the house was purchased 20 years ago. Her sister told her to put his name on the deed and she did. 

Is there any way around her son? Or what would you suggest I do to close this deal?