The roof is only 6 years old. 2 of the HVAC systems are newer, 2 are older.

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Part of the property description states it's been renovated and all systems work properly.

I had approximated the remaining useful life of each major house system and the approximated next replacement date and backed into a $423/month reserve for both units ($211/unit).

For example, create more natural light on the interior or develop a better drainage system to move water away from the home. 

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@Denise Chester It would depend on where the system is located. 

I finally have my systems in place and would like to acquire 6-8 more properties this year, but this is putting a hitch in the plan. 

I was using the "class" system based on quality of tenets/safety of area/stability of area vs. more of a classification of the income/town itself...but I guess I could have said more of a A- minus compared to towns like summit :)

But probably defendable in that a shared ventilation system will create an issue for other tenants no matter how 'good' it is.If the only reason is they rented a 'pet free' place then no, absolutely there is no defense and you best let that service/ESA in.