How much do you need to clear per door?

[Arthur Banks]

How much do you need to clear per door to consider it a deal? I'm looking at my first property and accounting for management cost (10%), the numbers (provided I'm not over estimating costs) aren't too appetizing. Managing myself, I'm looking at about $135/mo cash flow. I've heard $100/door is good. I do plan to manage as it will only be one property at this time, but I'm looking at the bigger picture.