Drop by for a quick inspection on a regular basis, watching for things like broken windows, tampered locks or any other signs of attempted forced entry.2. 

Has happened, but I try to accept when the user has made an attempt at being cordial. 

Conventional is 25% down for 3-4 units owner or non owner and 30% down when you hit the 5-10 mark (min 720 fico, 6 months on all 2nd/non owner properties reserves, also).You can attempt to move from 4 plex to 4 plex if you can structure the file well enough for the primary occupancy to make sense but it will be tough as they will start to get the trend as you go to buy your second 4 plex with "owner occupied."

Is it possible the seller is attempting to set up a 1031 exchange where he or she would have to identify a replacement property within 45 days of the sale of the existing property ?

I've sent a letter to the family attempting a sub to, but with no response, it is looking like a trip to the sherrif's sale. 

Also, you cannot engage in real estate negotiations on someone else’s behalf or even attempt to conduct a real estate transaction for another person or organization unless you are properly licensed.Source:  http://www.criminaldefenselawyer.com/resources/brokering-real-estate-without-a-license.htm

The agent finally got back to me after many attempts and notified me the properry is now under contract to another investor for $1,100 over asking price.And Will, we're on to the next one!

I would discourage you attempting any option besides hiring a contractor to rehab like your original plan. 

With respect to that, I am attempting to balance the JUMP IN NOW urge with the 'analysis paralysis' BTurner and JDorkin refer to in the BP podcasts.T-minus three months... goal/deadline for going under contract on an investment property.

As I do so, and attempt to crunch numbers and look at listings for practice and to get a sense for the market, I'm running into some walls in my theoretical business plan.I will have the resources in the next few years or so to get a conventional mortgage on maybe 4 single family homes that are worth about $200,000 each, standard 20% down.