You provide a few common areas/community features (Laundry area/meeting room/garden/aquaculture/greenhouse), and they pay an HOA fee for that and other stuff.

The best way to answer this question is to look at the square feet of the home and how many can comfortably fit in the common areas...i.e. dining room, living room, outdoor spaces, etc.

If I could do that, I might get the property for what I'd originally intended, plus the owners would get some badly needed money instead of a big fat NOTHING by losing it in the auction.  

However, I see those aren’t very common in that area.

Subject-To financing is not super common here, especially for condos/co-ops. 

Your strategy of starting with fix-and-flip projects to generate capital and then transitioning into mid-term rentals is a common and viable approach.

For example, in my area garbage and sewer are the most common municipal utilities and thankfully flat fee that I can bake into the rent. 

Yet, you can do online searches and, most importantly, use your common sense.A few days ago, one of you asked me what I thought about a particular development in Tulum he was thinking of buying into.

Unfortunately, common spaces that you use as part of your personal space can't be included in the rental portion calculations. 

There are lockable thermostats for commercial use, but I can't see that working in a rental.I think the main issue will always be that any thermostat that you can set a minimum temperature in will always be susceptible to this fail safe failing, due to the possibility the tenant could change it on purpose or on accident.I'd hope in a 4 plex as long as there is no building defect to the thermal envelope that it would be difficult for one units pipes to freeze as long as the other units were occupied, seeing as they share some common walls/ceilings.