Sounds like a prison. Better add a substantial budget for riot control. Might need some confinement rooms too. About 80 percent of the illegal migrants are single military-aged men. Many are experienced criminals who have been turned out of their home country prison systems by their governments. They won't be easy to control in large numbers in confined spaces.
Cheaper to just build concentration camps (err... "resettlement centers") somewhere out on the plains. And that may very well be what we end up doing.
The property owners are going to lose their shirts. The regional banks that hold mortgages will likewise fall. The larger megabanks have enough clout to get generous federal program loans or grants and will buy up the vacant properties at pennies on the dollar. Some properties will literally change hands for one dollar.
There are a lot of possibilities when you can acquire large tracts of land for one dollar. Who cares what building was on it.
Your comment about "figure out a new scam to trick investors" is right on the mark.
Commercial buildings may not be suitable for conversion to residential property, but will that stop the government from spending thin air money on such projects?