You subtract that number from your sales price less closing costs, and you have your capital gains that would be realized on the sale of your primary residence.  

The $9K of net cash rent left over after subtracting expenses and interest is still jingling around in your pocket.Rent: $30K - expenses ($12K) - interest ($9K) = $9K of net income that you pay no taxes on.  

Subtract housing units by the number of families in the city.

Subtract your costs, you left with $16k.

Then you subtract $9,500 to arrive to $500.

The calculations seems to subtract any 2nd from total acquisition costs from the first, down pmt, etc.  

Well if comps are around $245k then you need to estimate how much the remodel work will cost, add 25% to that number and subtract it from $245k. 

Arv * .75, then subtract repairs.

I've decided to pay the electric bill and subtract the amount from the prepaid month, and notify the tenants that amount will be due for March's rent.

Revenue: Gross rents then subtract all belowVacancy(5%)-Maintenance-if it's rehabbed this number will likely be close to 0 otherwise, budget another percentage (talk to investors in your area)Property Management 8-10% - CapEx-5% for reserves and big ticket repairsProperty Tax-Insurance-Debt Service (principal and interest) =Net cashflow pre tax