Finally I add value to properties including fresh paint, new light fixtures, smart locks and even adding a kitchenette of laundry room if the landlord agrees that it will add value to their property to create a "second unit" out of a bedroom suite with a separate entrance. 

It's fascinating to see the diversity of responses and that there are equal amounts of perspectives on both sides. 

From Dan's perspective, John does not lose out on anything but Dan save's $500.

I have some perspective  as it was 3 years ago I decided to go self employed and count on no one but me, and investing has only grown compared to the w2 days.

This was a pretty big rehab project and took a few months to complete - however, with a $321,000 purchase price, this house is now worth $485,000 and I was able to recover a majority of the cash I put into the deal as well as go from 5% down payment to 20% equity all while owning a fresh new house!

A friend has kids, and they currently have three dogs, a rabbit, fish, a turtle in the house (not to mention the three ducks and six chickens for fresh eggs... of course, those stay in the back yard). 

Not only that, but the framework and perspective it gives on your business building/investing activities are the best I've read.

I'd like to put the marketing perspective on it. 

With the numbers people throw at me, in my area the TLDR/conclusion is most often that ADUs do not seem to make sense to build purely from a resale value perspective.

I'll offer the perspective of global nomad.