The lists are usually compiled through the licensing data and not all have an email on those files.

@Patrick M. 1) I second what @Theo Hicks said about contacting brokers. 2) Also, you may want to have a real estate friendly residential realtor contact as sometimes small commercial multi's spill over to residential MLS or the realtors may have contact on the other side. 3) In addition to that, you can use such sites as ListSource to compile your own list of owners with small MFH's and start direct marketing campaign. 4) Find local apartment owners associations and join them, as well as local MFH REI clubs on meetup and BP.

Here are a few more data points compiled by KCM - again national averages; I believe we may see quite different regional scenarios e.g.

You can also purchase lists and compile lists from city and county for 60-90-120 days late on mortgage, pre-foreclosure, delinquent taxes, water cutoff, code violation, probate, divorce, high equity, etc. and mail or cold call.Other methods are driving for dollars, door knocking, wholesalers, craigslist, Realtors, FSBO sites, expired listings, foreclosure sites, put out bandit signs, billboards, newspapers, other offline publications.You can use pay per click/adwords, facebook, Linkedin, Youtube, and other forms of online and social media marketing.

@May Emery I have a couple from list source and the other I compiled by driving fro dollars.

All kidding aside though; what seems to be the core values in an approach to asset protection...these 5 pillars you've pointed out went right into one of my specific spreadsheets of compiled personal data as I begin this REI journey. 

I'm a recent US Navy Veteran currently residing in California; and over the past 6 mths I've found myself 24/7 compiling all the statistical data I can utilize to dial in to which market I'll be breaking into the multifamily rental property game.

List segmentation can occur at most any point, both in aggregating and compiling data records as well as during and after contact established during a campaign.In my early years we did not have the benefit of PC's, so we manually vetted records based on a cursory eyeball decision as to their likihood to produce a profitable result.

@Michael Quarlesinteresting topic can you please elaborate on this pre NOD listwhat vendor is compiling and selling this list?

I'm beginning to compile a mailing list from listsource.com using many of the filters recommended by some of the experts on BP.