Similar to the comments above on using FurnishedFinder, also check Airbnb and sort for 30+ day rental options. in addition, I'd recommend talking to the local university and hospitals nearby by calling to their various departments.

That said, I'm grateful for the alternatives you present--you're keeping the bottom line in mind, so I appreciate your help in exploring options that achieve the bottom line for the investors. 

Due to the creativity of the deal conventional funding is not an option.

There are a lot of investment options.  

That property is now a reliable source of rental income and a constant reminder that success starts with taking action, learning on the fly, and embracing challenges head-on.

In any case, you can easily calculate that.Looking at your objective of retiring in Costa Rica, you have two options:1.

Taking out more debt does not sound like the best option IMO.

But if they don't willingly make the payment your only option would be to sue, and they have the upper hand to let the lender know about the sale possibly triggering DOS.

Difficult to defend places -- hillsides with limited transportation options, etc. -- won't be allowed to rebuild at all.

Sure, being a RE agent is an option.