Take this opportunity to upgrade your plumbing and electrical if needed. 

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

Great property, perfect setup for a duplex with separate driveways, entrances, back patios w/ storage, brand new roof, plumbing, newer HVAC, appliances, flooring, etc.

I do know it needs P/B foundation repair, new tile, and plumbing updates.

Or any clues on the document that would allow me to spot any major problem, such as foundation, electrical, plumbing etc.?

Since the lease was with both then you need to make the check out to both, to do otherwise would be making a legal determination which is what the domestic court is for, and where they can take their issue to resolve. 

If all your plumbing and electrical are in place that would reduce it some but not down to $20,000.

Well I believe that the incoming administration will in the first few week find ways to reduce regulation and increase domestic energy production.  

What is the condition of the roof, siding, plumbing, electrical, etc?

She sent a reputable plumbing company out and they gave us a $9000 bid to do excavating, repairs, etc. due to some roots getting in some plumbing under the house.