calculating cash flow

[Thomas Parrott]

im trying to make sure i have a ROUGH (i know it isnt going to be exact) estimate on cash flow

im just trying to make sure my basic formula is right so i can track the performance i have already had easier (i have not taken money out to upgrade properties etc so i am not putting that into my equation)

im also listing all costs as repairs just for simplicity (would include management fee's, legal fees, & other write off capable items)

flow before taxes = rent received-mortgage payment- insurance -property taxes - repairs

flow after taxes = flow before taxes + .25(mortgage interest+ insurance+ property taxes + depreciation+ repairs)

i say .25 multiplied by the sum of all of those listed because thats the money you are going to actually see, if you depreciate $3000 you arent going to see $3000 so its not really cash flowing into my bank

could this be an ok way to get an estimate, or are my theories wrong on how im calculating this?