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%.

****I am not a financial advisor or guru, I was just a dumb civil engineer who learned that you cannot push on a rope and dirt and water  = mud.

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

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

Fridge filter is like a lightbulb it is a consumable that they can get or not get, makes the water better or I suppose the fridge smell less but it is not essential.   

Quote from @Natalie Allie: If you are still considering the Land Bank in Detroit listings, just be careful to check with the city on whether or not the water needs to be reconnected.

Also consider your lifestyle and if you want to be traveling 3 days just to check to see if a water heater is installed correctly and your property manager is looking after your property.

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?

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.  

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