@Ryan Sasscer, I can send you a spreadsheet perhaps but..
You are correct on the first term of cash flow in your rent less:
P (below) principal and interest per month
less Insurance per month
less real estate taxes per month
less reserve for rental vacancy (perhaps 1 month per year? or ~8% or rent
less reserve for repairs, perhaps 5% of rent
less Capital Expenditures reserve, perhaps 5-10% or rent.
Multiply by 12 months to put on a yearly basis.
That cash flow divided by you down payment and closing costs = ROI or cash on cash return
Next you need to know how much 12 months of mortgage payments actually pays down the principal on your loan.
Loan, L - B = first year's principal pay down. see formulas below.
P = L[c(1 + c)n]/[(1 + c)n - 1] = monthly payment of principal and interest
B = L[(1 + c)n - (1 + c)p]/[(1 + c)n - 1]
B is principal remaining after n monthly payments. for first year, n=12
L is your original loan amount
c =monthly interest, yearly interest rate/12
p= monthly payment for Principal and Interest
Now your next calculation is you ROI based on tax savings.
Your depreciation allowance is the purchase price + a few items of you closing divided by 27.5 years. check IRS for how to determine you initial Basis or value to be depreciated.
Now you can calculate how much of your rental income is taxable
the net cash flow from first calculation above + first years principal pay down(you only deduct interest paid)+ Capital reserve (hopefully you will not spend this the first year) = your best guess at taxable income from your rental. (This assumes you used you estimate for vacancy and repairs.)
No determine your tax rate for Federal and State from last year. Say it is 30%
multiply the taxable income from the rental by you tax rate to get the next tax saving or tax expense from this calculation. Add this tax (+/- )number to the net cash flow and divide by cash invested for
after tax ROI
Next step is consideration of principal pay down. The first year is the smallest number of your rental investment, so;
Add the principal pay down to the tax savings/expense and the net cash flow.
divide again by your investment to get the ROI at this level.
Lastly decide what appreciation you might expect. multiply that by the purchase price to get a yearly value.
Add this value to the last sum of cash+tax+principal pay down to get a yearly return estimate then divide by investment for total expected ROI.
Easy to set up on a spreadsheet, difficult to talk through!
Cheers,
Buddy