If the number are close[100k or less], do preemptive due diligence [water, sewer, stormwater, planning and zoning] if the property is considered for a new build development situation.

@Don Le first off, are you sure tenants pay their own water?

Most places its too expensive to have separate water and sewer lines. 

I just pulled out one of my policies, and it does cover mold and water damage.

RE may sound sexy to brag about around the water cooler but it isn't an especially easy way to make more than in the market and not at all passive in my experience. 

Taxes 5500/yr, insurance 5500/yr, water 2500/yr.

, things to add into calculations (i.e. duplex you cover sewer/water vs. single-family is on tenant, any other considerations?)

Some utilities stay with the house (eg water if the tenant doesn't pay, you get stuck with the bill), others go with the tenant (eg electricity, phone). 

I live on a very popular named lake here in MN, but it get's so packed with water traffic that it feels really small.

The faint water stain that becomes a ceiling leak?