... actually, as I skim over that report more and eyeball around a bit, I think I'm starting to develop a burning urge to strangle whoever wrote that report summary. Whoever decided to add up the results of compounding account errors -- which, from what I can tell from the HUD response and what the auditor(s) are actually saying, looks to be the primary problem with the total -- and present them without qualification or clarification is someone I would perhaps be willing to give a solid kick to the nethers on behalf of all accountants in the USA.
What seems to have actually happened of material note we could rely on, instead of possibly unreliable financial data and whatever the fuck was going through that auditing group's head, is that the HUD had a (probably not terribly major in any substantiative sense) problem with sloppy accounting, which when combined with system migration and the process of integrating legacy accounts into the system led to data entry errors, probably mostly of the misplaced decimal or typo sort, that when corrected caused compounding errors to propagate through the financial reports. The 500 billion value -- most of the discrepancies period, really -- appears to be almost entirely comprised of that, from what I can parse* of what the report actually says.
Basically, the numbers were wrong, but there doesn't appear to be substantial money or material actually missing, and what caused it, while there and needing redress, wasn't actually major and has mitigating circumstances besides. That huge amount was a data error, not a financial or management one (though there's issue with the latter overseeing the errors happening to begin with). If there's money actually missing, misused, or defrauded, it's probably a much, much smaller number -- the HUD itself says around three million (somewhere in the very rough range of about .006% of their budget over those two years) -- than what the report is intimating (and the news bits that are starting to kick up) even if it's being fairly careful to not actually say it.
... also, it's probably worth noting (both to myself, who was suspicious of the connection, and to those holding it as an achievement), that carson (and by extension trump's administration) had precisely fuck all to do with the audit, which was procedural, has been going on annually since somewhere in the 90s, was done under obama's presidency, and published the day before carson assumed the position. So for all those worried about either flawless accounting practice or possible fraud, say it with me: "Thanks, Obama."
*Though, to be fair, I've only got fairly low level accounting training, little field experience, and only basic introduction to auditing principles -- basically, there's definitely nuances and whatnot I could be misinterpreting or missing. Enough exposure to go, "Yo', hold up." without being entirely confidant they actually need to hold up, or in what manner or to what degree. That said, that report is very "Yo', hold up."