Immediately after I took over, tenants complained that there has been roof leaks that the owner attempted to fix himself, without good results.

The house purchased yesterday I spent day doing small projects-door locks, replaced a door, added alarm and home automation system for remote management, and fixed a leaking plumbing valve. 

I just completed the inspection yesterday and it seems the roof will need to be fixed(over 20 years, the boiler system is very old(there are 3 boilers), one of the 3 hot water heaters(HWH) is leaking and the 3 car garage (which is one of the main reasons the property is compelling as an investment purchase) is not structurally sound and may need to be demolished.

I just completed the inspection yesterday and it seems the roof will need to be fixed(over 20 years, the boiler system is very old(there are 3 boilers), one of the 3 hot water heaters(HWH) is leaking and the 3 car garage (which is one of the main reasons the property is compelling as an investment purchase) is not structurally sound and may need to be demolished.

The question I have is... it’s next door to a gas station.

I recently looked at a duplex and wanted to get some thoughts on if these items should be factored into the offer price:The water heaters were over 10 years old, both gas furnaces were over 10 years old, the water was not separately metered, the front porch (cement) had some cracks in it, and both units would need some paint and new carpeting. 

Technical answer: because a sink involves plumbing, including a trap which can leak sewer gassesReal answer: Because the city are greedy, in addition to incompetant.    

It's an oil/gas/agri town about 2 hours from a major center.

Hey guys, I have some tenants who have been giving me problems since they moved in, and just recently have notified me that the ac (located above the master closet ) is leaking into the closet ceiling.

You did not specify electric or gas or the size of the unit by I use them often because:-For smaller units they are cheaper and easy to install-Take up very little space-Are efficientThe negatives:-May require a breaker reconfigure as the usually require 2 30amp breakers-In bigger properties with a long run say to the other side of the house, it takes a minute or 2 to heat up