Nothing spells trouble more than one unit having the heating/AC controls for BOTH units.This property is in Denver County.

If you have zero vacancies, zero tenant damage, make sure utilities (especially heat) stay on every winter even if the tenant doesn’t pay.  

I needed $35,000 for a new heating system so the bank gave me $28,000 (80%) in a business loan for 60 months which has no prepayment penalty.

And now pipes froze cause no heat, and now it's $14k more to fix pipes, I gotta walk away" and "seller" says "like hell you will, you destroyed my property, you messed up my credit, now I'm getting foreclosure warnings from bank, YOU CHEATED ME". 

And if you do not think you will get caught, a lot of nosey neighbors will call you out on it (we did not rent a basement but we had built a shed as an outdoor dog house that was heated and air conditioned and someone called about that on us...).

In the summer while the other half of the country is dealing with sweltering heat, i'm still hanging at the beach.

Updates of heating, adding cooling, and electrical.

I looked at something similar about a decade ago which was some camping log homes in upstate maine which was a beautiful place but the place did not have power (only generator) and heat was via fireplaces.

We have also completed some exciting improvements including retyring a boiler for heat/cool ductless mini-splits and 9 units being electrically updates.

You are trying to build on a very fluid and shaky foundation.