They are very predictable.

What type of jobs do people work, look for clues at how much of the population is dependent on public assistance.www.movoto.comI started doing this when I purchase properties and find it is very accurate at predicting the desirability of the neighborhood and the quality of tenants that will want to live in your property.

Also Realtors are not a good barometer to use for predicting rental income.

I've also read that other countries are selling U.S. debt/treasuries and more economists are predicting a recession.

With foreign money coming in and buying property, and with predictions of the Canadian dollar to stay at a constant value of ~$0.70USD, property values may continue to rise.   

I was curious about previous real estate cycles and came across this short article: "How to Use Real Estate Trends to Predict the Next Housing Bubble", by Ted Nicolais (2014).http://www.dce.harvard.edu/professional/blog/how-use-real-estate-trends-predict-next-housing-bubble I am wondering what you BiggerPocket REI's think about the current trend.  

They don't expect you to be able to predict the future. 

I'm sure there are some that are great tenants but the lifestyle in my opinion makes for predictably bad tenants. 

I'll stick with my above prediction.

I am predicting 15-20% of gross.