Your fixed costs could be something like the following: $5k property tax, $2k insurance, $3k utility (including internet and TV), $2k landscaping (mowing, weeding), $2k or $3k maintenance (if you have a pool or hot tub). 

It's not just shorter-term downturns to be aware of, real estate just like the stock market can experience 10 year periods of no growth. https://fred.stlouisfed.org/series/csushpinsa

IE the flipping shows that used to be on TV and then you had the big mentor programs teaching it  ALA Montalongo  Vertucci  etc.  

You do not need a separate LLC for each property or a series LLC!

Also, I'm stuck with out-of-state investing which brings a whole series of risks with minimized financial upside (in my opinion) 

Rates are NOT high right now historically speaking. https://fred.stlouisfed.org/series/MORTGAGE30US   Sure, we have gotten used to historically anomalous low rates, but that does not mean we will get back there without the economy slowing down.

I recommend you find a way to give these animals away before you lose control and end up on a reality TV show.

Not a book but Robuilt series on YouTube by Rob Abasolo and AirDNA Podcast are great.

But, selling “cash flow” works for other industries, such as oil and gas production, music royalties, tv syndication rights, and probably some more I’m not aware of.  

To avoid the risk management/insurance that comes with tenants' wood fire use:I'm thinking to seal the chimney cap on roof and run a cord putting an electric Infrared heater fireplace in there, so they can still open the glass and get heat and watch TV over the mantle, but can't burn anything or have any flame.