Contractor put a small hole in the roof and it took me 3 months to get $200 back from him.

My hot water heater has a leak, I had a plumber look at it and they couldn’t find the issue.

Seller, I can only pay you $125k for it to work for me, but I really think you could get $160k on the market, net of $145k+ after costs of sale since you really only need a roof and XYZ to be a great home.  

As to the damage, you will have to prove that something HE DID caused the leak and not something HE DIDN'T DO.

From local rehabbers I have spoken with, the rough estimate they have used would put a full gut rehab with a couple of major items like Roof, AC, at 35 per s ft.

The property is in overall good condition but may need a roof ( around 10 K ) within 2-3 years.

Defects-Deferred maintance (roof leaks, windows rotting out, mechanicals not workings) must be considered. 

I thought I had a leak but have had the whole system looked at and nothing was found.

He then let me know that no obvious sources of a leak are known of in the home and no evidence of leaking is happening, but the high water bill is an indicator of a leak somewhere.This brought up a fundamental question that I wanted to put out to you and learn from you on:  if the tenant pays the water bill (it is in their name with the city) and there is  SUSPICION of a leak, who's responsibility is it confirm (and pay the fees that would be associated with confirming and/or finding the leak)?

I purchased a serious value add 12 unit apartment building in Indianapolis in April of 19' and spent the last 9 months completely turning it around:- Over $150k in renovations: new roof, completely updated common area, most units renovated and turned, new furnaces, plumbing and electricity updates.- Went from 9/12 units occupied, mom and pop managed and  all well under market rents and most not paying on time.