I'm trying to understand how capex reserves factor into NOI, Cap Rate, Debt Service Ratio, and other metrics. Lets assume the following yearly numbers for a Single Family Residence (these numbers are made up, try not to get hung up on the minutia)

• $200,000 - Total price of property (purchase + rehab; aka ARV)
• $24,000 - Gross Income (from rents, no other income)
• $1,200 - Vacancy (5%)
• $3,000 - Property Taxes
• $1,000 - Insurance
• $1,000 - Utilities
• $2,000 - Maintenance/Repairs (1% of total property value)
• $8400 - Debt Service

As I understand things, my Operating Expenditures (Opex) will be:

      Property Taxes ($3,000) + Insurance ($1,000) + Utilities ($1,000) + Maintenance ($2,000) = $7,000

Now to calculate the Net Operating Income (NOI):

      Gross Income ($24,000)  - (Vacancy ($1,200) + Opex ($7,000)) = $15,800

Once I have my NOI, I can go on to calculate the Cap Rate (Net Operating Income / Total Price of Property = 7.9), the Debt Service Ratio (Net Operating Income / Debt Service = 1.88), etc.

What I am missing, is my capex reserves. I know someday my property will need a new roof, so I set reserves aside for each property. I typically set aside between 10% - 15% (depending on the age, condition, location, etc). I don't understand if the capex reserves should be excluded from these types of calculations, or if it should be included somehow?

Thanks