I have seen a few ask for data. So here is some of mine. Evaluating 6 properties over a 10 year period, I have experienced an expense of 35%. That does not include depreciation (non cash) or mortgage (principle and interest).
It also does not include capital expenditures. This is really what I was missing. New capital expenditures come through with depreciation, but are not reflected in the 35% above. I will do a quick review of the capital expenditures over the same period to see if it totals 15%. It may not reach the 15% number, but I'm sure it will be over 5%.
So, I guess I should say that you have converted me to the 50% rule. I would tend to agree that a rule of thumb expense rate of 45 - 50%, which would include any over time capital expenditures, is probably accurate.
Of course, for the purpose of investment evaluation we also need to consider gain from appreciation (???) and cash flow after tax. Appreciation is probably irrelevant to me since I tend to buy and hold (It is relevant, however to my kids).
But I think the tax effect is relevant to all. If you don't have to pay them to the state or feds, its real dollars. I think that anyone earning over $50,000 with their day job will benefit to some degree. Someone with even break even cash flow using the 50% expense rule will most likely come out with a positive cash flow after tax.
So, the follow on question would be what simple metrics would you use to evaluate a property after tax (let's say using a 25%, 35%, or 45% state and fed marginal rate)?