SITUATION UPDATE: Ex has my our 4 year old Mon evening, Tue, Wed, Thurs, Fri and I get him Sat afternoon. Fighting for joint custody. It's been this way since she left in October. I'm trying to refiance the house; We're both on the title to the home and she's refusing to come off. She's asking for (and entitled to) child support from the date of filing. My question is: is she responsible for half the mortgage for the time she's been gone? I'm curious if I can have what I owe her in retro child support offset by what she's 'responsible' for in the mortgage. All comments would be greatly appreciated.