Ok, I am very new to this so if I am way off I will not feel bad if someone slaps me into place.
I can see the argument that Scott Gives and the one that MikeOH gives. Both are very well put and to me it seems that they are both right.
Let me explain what I mean.
If you have one rental and only one rental that is a new 1 year old townhome your expenses may very well be quite a bit under 50%. I actually have just one rental and I have spent 120 bucks over the last 6 months.
Now once a person gets going in this business and starts getting more properties I think the number will head towards 50% more. Some place will need more than 50 and others will need less.
I think I am correct in saying that with all the rents a person brings in that no one separates the 50% from each check and puts it into an account for that one home so that it can be used for only that home. That would not make sense.
I would thank that if you actually did the 50% rule and put that money into one account you would be able to cover any expense that any property would need and some will need more than others.
So in a way every property is going to be different, but when dealing with a large number of them it may be better if not easier to go with a set percentage.
Anyway I am just a newb and may be way off base.