I see these four rentals providing us a regular stream of income during retirement. 

It's important to go there in person, at the very least do video calls if you can't fly out and be in regular communication with whoever is working on or managing your property.

The purpose would be to rent it out through a property manager just like a regular single family home.

Competitive upfront costs and ongoing subscription costsPlus 2 Nice To Haves: Good analytics reporting and Compliance Updates regularly communicated

I am a regular lender doing FHA, VA and Conv, but I also loan my own money privately, and pool money from other investors when I don't want to loan my own money.  

Or is it a regular house in a neighborhood?

I'm a landlord of a 3 unit building and a regular check on it and clean the hallways lately.

Most of the other regular costs associated with the loan apply... appraisal, doc fees, county taxes, etc.  

Because a payment plan is spread over a period of time, I would keep the owner updated regularly until the plan is complete.Again, I operate this way because I'm detailed, everything is documented, I'm confident in my process, and my owners know I operate with their best interest in mind every time.

A quart of regular milk is about 1 Euro, grass-fed organic milk is 1.10 - the difference is very small. (1 Euro = roughly 1.1 USD) Here in Milwaukee I pay about about $7 for for a 2 quart container grass-fed.