This far the mechanics of what he is doing are clear to me.

@Fahima Hilal an architect usually only outlines mechanicals, plumbing & electrical on their blueprints.Your contracts should be creating appropriate drawings showing where their stuff would go and submit to city with their permit application.

Are the separate mechanicals for each unit? 

I should have also added that the reason I am pulled towards real estate as a wealth generating mechanism (I.e. the appreciation aspect) is that I bought my first house with ~$20K of my own money in Baltimore (supplemented with 6K of grants), bought at the right time and did a little fixing it up, used the proceeds from sale of Baltimore home to get into the lower end of the market in quickly appreciating Seattle.

When the rental was published, they added a mechanical lock with the house keys inside.

But larger repair items such as appliances and mechanical, plumbing, electrical, roof windows doors etc should still fall under the landlord's responsibility.

It might be a value-add for prospective tenants to know there is a mechanism in place to leave early.

Need to put the windows and doors in, and then start the mechanical rough inside.  

All of the mechanicals, including permit dates and any identifiers.

Once those are complete, rough plumbing, electrical and mechanicals can be started (rough plumbing should go first, then mechanicals as these are the larger sized items and rough electrical is easier to work around them than vice versa.