Accurate rule of thumb?

[Joshua Andrews]

I recently read about a rule of thumb for apartment investments and I'd like some BP member feedback.

The rule of thumb goes like this: "For every one million dollars of real estate you own, it should be cash flowing $2,500 per month."

This number seems a little low to me, since you would have to own a ridiculous amount of apartments to ever set yourself free financially.

Has anyone heard of this rule of thumb, and if so what are your thoughts? It's not making a lot of sense to me when I run the numbers.