It's always dangerous to pay debt with debt. 

She exposed her children to this danger.

Mold is a problem and can be dangerous.  

I distinctly remember one advertised 3-plex where they said the annual expenses were something like $1800.

I'm looking to buy a few rentals in Kansas City in 2019, but am frequently warned of the dangers of out of state investing.

Dangerous some as many don't understand it's not comparable to say the APY on the basic CD.

Otherwise, it is mighty dangerous, because everyone wants to be in expert in health, law and taxes, based on their extensive Facebook studies.Your friend has (correctly) heard that the new tax law allows Section 179 for rental properties.

@Frank Wong I agree it seems that too many people become used to the current condition to forget the dangers of being over leveraged.

Dabblers can be dangerous as they tend to not be experts in a specific filed and can make mistakes or overlook problems that can cost clients dearly.No legal advice given.  

While using tax benefits of the loss, yes, I would still save some money compared to renting / buying, but that seems like a dangerous wager to me given that the depreciation taxes will be recouped by the feds if I decide to sell and THAT could end up costing me way more than I ever actually made on the property.