It would be more ideal if you had or can find an investor friendly agent there to rep you as the buyer to ask all the questions or know what questions to ask for you to figure out more about all four units. 

I have done quite a bit of studying and research over the past year and a half, and I've recently started reaching out to potential cash buyers in the area.

A lot of lenders here that can help you more than I however I broker a lot in FL and most of my buyers use (in order)1.

If you haven’t done so, join AZREIA or smaller local meetups, where you may meet investors (who ought to be repeat buyers).  

Plus I continue to pay for leads that are not my avatar (aka flippers and STR buyers). 

This means a lot of units are sitting, and we're seeing a lot of price reductions, lower offers being accepted, sellers willing to help cover buyer closing costs, etc. 

The rest is luck: did it rain that weekend and did we have the right buyers walk through the door, to push the winning offer just the last bit.. you can't control that. 

If you flip again make sure a legit company does it to help ease future buyers

Scotiabank is the most popular bank in DR for foreign buyers. 

How have you gotten aligned with your co-buyers in the past (any exercises, tools, resources, processes, etc you've used) and how might you do things going forward?