Behind referral on on-line sources like Next door, Google review, FB marketplace, etc.  

I highly suggest you use our marketplaces to find trusted, investor-friendly team members: Tax Pro finder: https://www.biggerpockets.com/business/finder/tax-and-financ...Lender finder: https://www.biggerpockets.com/business/finder/lendersProperty manager finder (if you go that route and don't self manage): https://www.biggerpockets.com/business/finder/property-manag...

One tip is too is reaching out to some people in your market place that are doing flips and see if they can send you their spreadsheet they are using.

If it’s verbal, they’ll need to document any prior communication or payment records to establish the relationship.If the PM is completely unresponsive, they may want to send a formal written demand for communication and payments via certified mail.

H there, I'm a certified international property specialist and while i don't personally specialize n Costa Rica,  have several colleagues who do.  

Are you a Certified Property Manager?

I would start with the marketplace section here on BP. 

They would also give the buyers more confidence as they're a certified and accredited vendor rather than a mason contractor.

This property has some one-of-a-kind qualities namely a nice creek with inbound and outbound waterfalls at each end of the property (its on a hill w creek canyon).I've gotten the septic scoped and certified, well is good, power needs to be reinstalled as property was abandoned years ago.

Inspections are typically done by licensed professionals like structural engineers, architects, or certified building inspectors.