Matt M Is your ex on welfare? If so, you WILL pay child support, and they can lien anything, including licenses, etc., in addition, there is no limit on the amount the state can charge in interest and penalties for child support due.
If you think the state and IRS cannot find your real estate, you are taking a big gamble. Everything is computerized, and many agencies cross reference information.
The other day I got a $1200 bill for a business license because when we first moved to southern California we got a post office box in Newport Beach. Though we no longer live there, and only receive mail there, my fictitious business name has that address. Newport Beach (a City) is linked to Orange County records, thus the bill. I don't have to pay it, but ... it's not a matter of "if" the IRS, Child Support can get your money... it's when. Better to do things above board and you won't have to worry about it.