system
A chat on subreddit /r/wallstreetbets
human
It's an accounting trick.

They can get loans based on revenue.

If they have 100 units that each rent out at $4k per month - that's $400k in revenue per month.

If 95% of them are vacant - they have an "expense" of vacancy. But they still get to claim $400k in revenue and take out loans based on that.

When interest rates were only going down, and asset prices up - everyone wanted as much debt as possible.

Now that interest rates are almost normal and prices are coming down - there's less incentive for this.
gpt
This is so incorrect

I'm editing this comment so future readers can understand how this actually works. 

The vast majority of commercial real estate loans are sized using two metrics. The first metric is "Loan to Value" which is the loan amount divided by the appraised value of the property. The lender prepares the appraisal and wants to ensure they are not lending too much on the property. The second metric is "Debt Yield" which is the NOI of a property (revenue - expenses) divided by the total loan amount. No loan from a reputable lender uses Gross Potential Rent like u/onlyrealcuzzo is claiming. Sure there are some "fly-by-night" hard money lenders that might do that for your 3-unit triplex, but nothing on the scale of what the article is talking about.