Half inch plywood.It's nearly reasonable to assume that if the sliding glass door is broken, the entire frame is coming out.

From my walkthrough, I knew right away the big ticket items we needed were a new roof, new plumbing, new upgraded electrical, new garage doors, and new AC unit; along with the standard refinish of the interior. 

Like upgraded electrical, heating, ventilating, air conditioning, plumbing, ADA, etc...Where this comes into play is if say a tenant of one apartment unit sets his unit on fire, burns it up and now you have to go in to rebuild his unit. 

Hi BiggerPocketers:Howdy all? Here is my situation.Current primary home (A) has 440K loan at only 3.6% 30 year loan. The property shows a zestimate of 1.5m though for all practical purpose it will probably go for 1.3m...

But as of now the cousin and the girlfriend have broken up.

The home has to be livable, before the cosmetic upgrades that are being added.

I probably should add in some test since the property is over a hundred years old (built 1901), plus may need extensive upgrades (to HVAC, Plumbing & Elec.).

5 day should be first then the lease is officially broken by tenants, then you can negotiate a new lease new rate including the second tenant if approved.

(its the buying at 145k with an arv of 150k and needs 15k of upgrades and 15k in repairs, and not having the RE license, and it rents at $1200, starts to feel the pain) 

The cities like this around me tend to be lacking in infrastructure and internet/tech upgrades as they have been mostly left behind with the loss of tax revenues in recent decades.