Does the 50% rule work?

[Jill Herges]

I am just wondering if the 50% rule actually works?  If I factor in actual expenses and use 10% each for repairs/maintenance, management, vacancy and Cap Ex that gives me 40% of rents right there.  No way I can pay taxes and insurance for another 10% combined in my area (taxes are high).   I am wondering if I am figuring too high by using 10% each?  I have been looking at possible deals every day and I can't make any of them cash flow by using those percentages.