Yes, gross rent. NO Rental Agency = 0%. You do not need a rental agency. It much easier and more painless without a rental agency. Sorry to the advertisers. Also, most rental agencies charge much less than 33%, more like 20%-25%. Lastly, you have to take in the effect of the paper depreciation losses on your taxable income. I believe you could gain a taxable benefit of up to $25k per year.
Talk to a good realestate broker and enlist a good CPA, before you decide buying is not feasible for your situation. Good luck with your decision.
You can only deduct the depreciation and other expenses up to the amount of your rental income. So, you get no tax "benefits" other than the fact that you pay no tax on the $25k which I factored into my equation.
And, I disagree, using a rental agency makes things much easier for a landlord. A good agency takes most of the hassle out of renting--especially if you own multiple properties.