My child's father, whom I was married to, has back child support owed. He passed away a couple of months ago. He owned a home and property in Washington State. What legal grounds does my son or I have to collect the back support or the property? My son is his only child.

If there was back support owed, you can place a claim against his estate to collect that support. If you son was his only offspring, he may be able to claim a share of the estate if there was no will. So you need to find out the status of the estate. Check with the local county Probate court.

The child may even have a claim to the estate, and for sure can file a claim for support against the estate. I would hire a probate attorney to investigate the estate.