Rejected by more than two dozen bond companies, Donald J. Trump has so far been unable to come up with the nearly half-a-billion dollar penalty owed by Monday in his civil fraud trial.

Just days before the deadline, the former president’s social media company completed a merger — a move that is poised to pump an estimated $3 billion into Mr. Trump’s coffers. That is more than enough to cover the $454 million penalty that he owes to the state of New York, but the merger restricts him from selling his shares for six months, or using them as a collateral against a loan.

Unless those rules are waived to allow him to tap the infusion of cash, Mr. Trump faces the possibility that the state’s attorney general will move to freeze some of his bank accounts and attempt to seize his properties in the city where he made his name as a real estate developer.

The buildings at the heart of the lawsuit — several that dot the Manhattan skyline, like 40 Wall Street, as well as a 212-acre property north of the city in Westchester County — sit like the smallest figurine inside a Russian nesting doll, protected by layer upon layer of legal entities. Lawyers specializing in bankruptcies, foreclosures and corporate insolvency warn that getting control over, and trying to liquidate, any of the former president’s flagship properties is an uphill battle.

And even if the attorney general succeeds in acquiring Mr. Trump’s real estate, unloading a 60-story skyscraper involves a spider web of transactions.

“People are really, really good at litigating and getting to the point of a judgment,” said Brad Eric Scheler, a senior counsel at the law firm Fried, Frank, Harris, Shriver & Jacobson, where he oversees corporate restructuring and insolvency. “But they never focus on the fact that collecting on a judgment is very hard.”