I assume it has sewer/septic, water and electric and they 2 tiny homes are plumbed/wired?

In addition, I will also be paying much closer attention to water flow patterns and signs of erosion around our next investment!  

If you have a 6 bedroom in an area that does not have a university (students looking for shared space) or is in a family friendly place it may sit vacant longer between tenants.For Capex, try not to use a generic number - look at the roof, furnace, hot water tank, kitchen - when will each need to be done and what will it cost?

The rental might be vacant for a month,(8% loss) or a tenant might not pay for a month while you pay to evict them.(8-16% loss)  A $1,000 appliance/water heater, or a $8k rook or hvac unit might go out.(5-40% loss)  You should be paying a PM 8%.

Its extremely important when running tighter margins like what you're talking about to focus on age of HVAC, water heater, appliances, roof, etc.

Given this is where my major operating expenses fell (beyond taxes and insurance), keeping this cost lower, by average, helps my cash flow.I invest in older neighborhoods, so the 2-4 unit properties, typically have single water meter, maybe single electric, and many have radiator heat with a single boiler.  

What we do for houses with heating oil , we measure the amount of oil in the tant ( There is a chart that tells yo how many inches equals gallons ) And the tenants pay that up front when they move in , the oil is now theirs .

An alternative to batteries is a "water battery". 

That certificate would show open taxes, water, housing violations, citations, condemnations, receiverships, construction liens and other municipal liens.

You might need a 2nd well if you're not on city water.