In addition, markets are volatile now and very hard to predict your ARV.

For example, in the ghetto the growth prospects are generally not as good and the tenant quality is generally lower (which can lead to more risk and more volatile cash flow) ... to compensate for this limited upside and added risk, the market prices these properties lower in comparison to the rental income they are capable of producing on paper, resulting in a higher CAP rate.

Some governments may ban it and we will surely see more volatility as we go. 

I don't recommend a lady ever meet a potentially volatile situation or person alone.  

Tough to get a secured investment at 6% or whatever in this environment with banks paying nothing and the stock market being volatile.  

If we were in the stock market, this would be the time we switch from high volatility  and rebalance the portfolio to nice, steady bonds. 

Too much volatility to make a great investment. 

And without the money in the market, it cannot benefit from the volatility that has recently created the losses, but also has the ability to create very large returns in short order.

Is there an index similar to VIX (volatility of stock market) for real estate?

This leads to less volatility in the asset class since developers don't get caught off-sides and flood the market with excess supply.Like all real estate, location is paramount.