I think a sort of Mechanic's/Construction Lien on the property would make sure they get paid because nobody wants to trade houses that liens on them at full value. Not only that, you can even force them to sell the house to recover the debt.

Not only that, the debt could get traded to someone that isn't barred from putting liens on things creating a sort of market for debt. This wasn't going to fix undocumented people working, it was just going to create a new industry where needs are met and debts get paid. Typical politicians, they create a law with a stupid intention and get unintended results. Same story as always.