The number 1 necessity of being a real estate investor is money. 

I'm very strict and picky because the income is just bonus money, not a necessity to pay mortgagee.                                                                       

In my market, cable and wifi is a necessity. 

@Michael Greenberg +1 on the electronics.  6 years ago an HDTV was not a necessity. 

I like your idea of having an exit strategy - that is a definite necessity.

A dependence on the people is, no doubt, the primary control on the government; but experience has taught mankind the necessity of auxiliary precautions.James Madison writing as Publius in Federalist 51

Let me say that againAll properties cash flow.Now if you are leveraging the property, that does not change the underlying fundamentals of the asset, but rather it is you the investor by choice (or in most peoples case by necessity) that creates a negative cash flow situation by adding debt to the equation. 

If you are happy spending $100 a week on the necessities, that price point is going to be a lot less than if you require $500 a week for the same level of happiness.I think what you really need to understand to answer the question for yourself is:A. how much do you spend on average to maintain your current lifestyle?

@Chris Eidson, CAPEX reserves aren't cautious, but a necessity. 

In an ideal world market forces would be left alone to determine technological winners and losers but the reality is that energy is the farthest thing from a free market one could imagine so some of these policies are reactionary by necessity in order to create solutions to real problems.