to be an actual fix and flip investor / business  its quite capital intensive.. and just a down payment is just a drop in the bucket of the capital required.your best bet is to put a little private network together if you really want to do this.or get your license and specialize in finding these types of properties for fix and flippers.. make a commish selling it for them.. and then the list back.. that's what agents in our market here do and they will knock down 250 to 500k a year no sweat in commish with no risks of borrowing money or a flip that did not work.

You are, in essence, trying to develop your own market assessment by utilizing shoe leather, door knocking, and some technology. 

@Robert Burns In my experience:#1 Calling FSBOs#2 Door Knocking About-to-Expire or Expired Realtor Listings#3 Mailing all Realtor Listings#4 Calling or Door Knocking the General Public#5 Advertising Online

Paying our lawn crew to door knock homes with high weeds/grass in targeted neighborhoods.

Does anyone have any wisdom on how to efficiently leverage this info when approaching a seller via letter or door knock?

Door knocking and "driving for dollars" are two of the best for wholesalers. 

Job market is tight, paid fairly and consider if you would do the job prior to knocking down the price. 

When I re-roof I knock the chimneys right off. 

Certainly not knocking  what the RE agent Sam said here from California about people having hardships and maybe their car broke down but are you kidding me?! 

Go to REI meetup groups, put up some bandit signs, do a direct mail campaign, start calling people, go door knocking, just do something to get yourself out of your comfort zone and start working.