But my guess is to the reason why people who own a duplex and if they are an investor they don't worry about the mortgage because they have the tenants paying the rent which pays off their mortgage and also have extra left over (cashflow).

It's extra money again, but more likely to last longer than Formica.

Of course looking at data leaves out some details for example it seems plausible that units with the extra half bathroom may have slightly better finishes than the property without the half bathroom. 

The reality is the opposite - if it's not in writing then the PMC doesn't have to provide the service or can charge extra for it!

Do you need the extra for the refurb?

Ensure the plumbing and electrical connections are regularly checked for any leaks or faults.Lighting and Fixtures: Modern light fixtures and ceiling fans add aesthetic value and comfort.

. $600/yr in taxes seems like a low amount for a developer to not want to pay in order to acquire an extra plot of land that would enhance their space lol. 

If he doesn’t pay then raise rent an extra $100.

I think the actual settings will vary if you are managing directly on platform or using third party softwares, etc.As mentioned above I think risking going vacant over a major holiday will outweight the extra housekeeping cost.Also, I am not sure how much volume you are doing but do not pay cleaners extra for holidays. 

Even as a rehabber.In order to find success nowadays, you have to be willing to go the extra mile and do what other wholesalers won't.