I house hacked my first two houses before I'd ever heard of BiggerPockets but it wasn't until I did my first true investment deal, a 100+ year old home in a historic district that was a full gut rehab, that I really learned some of the lessons that I'd heard and read previously. 

:Class A Properties:Cashflow vs Appreciation: Typically, 3-5 years for positive cashflow, but you get highest relative rent & value appreciation.Vacancy Est: Historically 10%, 5% the more recent norm.Tenant Pool: Majority will have FICO scores of 680+, zero evictions in last 7 years.Class B Properties:Cashflow vs Appreciation: Typically, decent amount of relative rent & value appreciation.Vacancy Est: Historically 10%, 5% should be applied only if proper research done to support.Tenant Pool: Majority will have FICO scores of 620-680, some blemishes, but should have no evictions in last 5 yearsClass C Properties:Cashflow vs Appreciation: Typically, high cashflow and at the lower end of relative rent & value appreciation.

I personally would not choose to purchase residential RE unless my underwriting shows far greater than double the historical return of the S&p500.  

Everything else is, comparatively, a bit “noisy”.The job market has begun to turn away from historic lows with current unemployment brushing up against 4%.

I would say probably historic reasons. 

Here is a snippet from our book-First, the historical audit rate of partnerships (Form 1065) is 0.4%.

We have a no parties rule and Quiet Hours because we are in a serene historical farm community just 15 minutes from the heart of the city.

I prefer the user interface of propstream, but historically I've gotten better quality data from batch leads.

This is all historic, but I'd bet the fundamentals aren't too dissimilar now.

:Class A Properties:Cashflow vs Appreciation: Typically, 3-5 years for positive cashflow, but you get highest relative rent & value appreciation.Vacancy Est: Historically 10%, 5% the more recent norm.Tenant Pool: Majority will have FICO scores of 680+, zero evictions in last 7 years.Class B Properties:Cashflow vs Appreciation: Typically, decent amount of relative rent & value appreciation.Vacancy Est: Historically 10%, 5% should be applied only if proper research done to support.Tenant Pool: Majority will have FICO scores of 620-680, some blemishes, but should have no evictions in last 5 yearsClass C Properties:Cashflow vs Appreciation: Typically, high cashflow and at the lower end of relative rent & value appreciation.