He has so much coming due in some of his properties, he's actually way more in debt than just half a billion.
I'll let someone smarter than me explain the best tact, but it seems to be (if I'm readging this properly) that they should go after the properties that are already paid off...for starters, all the proceeds go to his debt, instead of dealing with partners and outstanding loans, etc. But additionally, those properties couldn't be used as collateral for further loans down the line. And all the other properties have major payments coming due in the next 5-10 years, which would make refinancing without collateral real hard.
The issue was that legally, Mar A Lago is designated in some way that it can't be a residence. Some of the locals there were talking about suing him for living there, hence the "property manager" or wahtever subterfuge they're using to prevent him from being sued. Because it can't be a private residence. Which is also ther reason it's valued at like 15 million dollars, as a commercial property, becuase actual residences areound there are much, much more expensive. Something else he's whined about.