If it produces more energy than it consumes then the building is Net positive - though Net Zero is too frequently used as a blanket term to cover both these cases.Ironically, Net Zero does not automatically imply higher energy efficiency - there are several examples of commercial buildings with large expanses of flat roofs (i.e. warehouse) which are net positive, despite the building itself being horribly inefficient.Building standards in North America are woefully outdated on matters of energy efficiency.  

Either you or a representative you trust with out exception must perform all the necessary due diligence just as you would for a property down the street from you.Turnkey companies want to maximize profit by doing as little work as possible using the cheapest materials.I would have a professional inspector check everything with a fine tooth comb,especially the roof,plumbing,electrical,and HVAC systems.Also make sure you get a repair warranty for when things go to hell in two years or less(and they will).I honestly don't trust any property I don't rebuild myself with my trusted contractor and quality materials that will last at least a decade or more

Sometime it also covers roofs, but not on this property.   

If anything we can call this practice : )Property is a side by side all brick duplex, newer windows and roof.  2bed1bath 800 sq ft separate basements and all utilities are in the tenant's name.  

Here is a part of the letter, I sent to the seller:The home inspection was completed on September 29th (please see attached) and the following issues were pointed out: 1.The wooden floor frame in the middle unit is deteriorating due to either prior water leak in the bathroom or due to moisture infiltration through the walls and foundation.2.There is evidence of significant settlement under the middle unit bathroom and north closet.3.The settlement of the floor and walls has also resulted in settlement of the roof frame above this area, ceiling shows cracks.4.There is an obvious depression on the roof – water is ponding on the roof above the middle unit, which adds excessive weight on the roof and potential for leaks.5.Asbestos containing material has been found.6.The current bedroom heat installations in the north and south units pose a safety hazard from carbon monoxide, fire and oxygen depletion.7.An electrician performing upgrades did not use ‘arc fault breakers’ in the north and south unit breaker panels, which is required by the national electrical code.8.Upgrades to the electrical system, promised by a real estate agent, have not been completed yet.

, what if something breaks i.e. a roof leak while the tenants are in there, who will pay for those repairs?

Now, you didn't mention CAPEX (expensive items such as roof, HVAC, hot water heater, etc.). 

We ended up having to do a lot more work than expected (including a new roof, water heater, pulling out ceilings, etc) and also did some work that wasn't "needed" like insulating and replacing the ceilings of the top floor. 

Middle class incomes CAN be used to create a lot of wealth if they save up enough to buy the first property, live in one of the units (now you can have roof over your head at no/low cost), which allows the investor to put less money down, etc.  

I was about 5 days from closing on my first place (an up/down duplex + cottage)...when the lenders (a typical residential / investment lender) said he would not fund the transaction...because the appraisal came back saying that it was a "raised mobile home" - and they don't fund mobile homes.It wasn't obvious that this was a mobile home by sight - apparently it was just the foundation of the mobile home that was used and then was re-finished (new siding, new roof, etc).