This is a long game and the market is dynamic in the short term. The long term trend is clear, upward. Cashflow is a derived number and can be manipulated. What is the cashflow of a building I own free and clear and have deferred maintenance vs a renovated house I have leveraged at 80%? There is more to the picture than one number. I generally stay clear of derived and theoretical numbers, vacancy, cap ex, reserves, cash on cash, cost to turn, maintenance and so on. I use numbers I can quantify, purchase, renovation costs, actual rent, tax, PITI, property management, principle pay down. I follow the KISS method. Keep it simple stupid!
Taxes should always be considered. Tax is a real number, it can be qualified and there is a time line associated with it, the fiscal year. Taxes, insurance, depreciation, maintenance and interest are all deductible. All of those line items are on sale 1/3 to 1/2 off depending on the rest of the individuals taxes.
I know it is a common accounting practice and a spread sheet requirement, but the idea of saving for Capex never made sense to me. What if I bought a building and held it for 5 years and saved for cap ex every month, kept the money in a savings account at .05% and inflation ran at 3%. First, the inflation would eat my lunch. If at the end of the 5 years of holding, I did not replace the A/C or roof, no cap ex. How is that money accounted for? It was actually cashflow, there is no cashflow look back.
Short of natural disaster and fire, there are very few surprises when it comes to the building, you can anticipate the expenses. You are doing well if get 20 years on a roof, 15 on an A/C. If you have older buildings and equipment, you are going to have expenses. I have a duplex with A/C units that are 20 years old and I may not like it, but I know they are going to fail. I will pay cash or put them on a credit card, depending where I am in my funding and build cycle. I do not have a rainy day fund for every building I own. I have operating capital and it is always moving. I do not let it sit on the sidelines. In any given month (year) a property may be unprofitable, but as long as the overall portfolio is performing I am satisfied.