I had a contractor tell me he knows how I can get a new roof with the installation of solar panels...anyone else hear of this? 

There is also a fantastic networking group in Chicago that does monthly events with panel speakers and all kinds of great intel spanning a variety of topic matters that change each time. 

I do have plenty of South facing roof space and I am thinking of installing solar hot water panels to preheat the water for DHW and the heating system. 

Electric: I recommend doing separate electric panels for each unit.

@Ashish AcharyaGive me a shout post 4/15.Right now I generally get on BP in-between clients to de-stress a little.Not a good time to get into a debate and dive into code sections.Perhaps my most recent example was too hasty reviewing the regs right now...The "-3" reg defines structural components by reference to Treas Reg Sec 1.48-1.The term “structural components” includes such parts of a building as walls, partitions, floors, and ceilings, as well as any permanent coverings therefor such as paneling or tiling; windows and doors; all components (whether in, on, or adjacent to the building) of a central air conditioning or heating system, including motors, compressors, pipes and ducts; plumbing and plumbing fixtures, such as sinks and bathtubs; electric wiring and lighting fixtures; chimneys; stairs, escalators, and elevators, including all components thereof; sprinkler systems; fire escapes; and other components relating to the operation or maintenance of a building.We know that a building and building structures are a single unit of property.  

The apartments are outdated with wood paneling walls, old appliances, old fixtures, and outdated carpet. 

It seems like it has the potential to be a decent house hack where I can live in one side and rent out the other side, but I am analyzing it as if I were renting out both units.Here's the overview:Seller accepted my offer of $90,000 (they were originally asking $95,000)Similar sized duplexes rent for around $1,500 total ($750 per unit)The total gross rent would be about 1.6% of the purchase price.I can get a conventional 30 year loan @ 4.5% interest, with a 5% down payment.Mortgage payments with PMI would be around $469 according to mortgagecalculator.org (not including taxes or insurance)Using the 50% rule of thumb to estimate expenses, I might be able to cash flow around $140 per unit.Here's what I found out when I went inside:There are 2 new forced air furnaces.Updated pex and PVC piping.Updated electrical wiring with separate panels.2 old corroded hot water tanks.

(new kitchen, bathrooms if possible, new flooring, and definitely new electric panels.)

So assuming your panel can handle the 2 double poled 40amp breakers it would be a lot less expensive than running a gas line & the venting of a NG unit.

When we first bought the house it was very outdated with wooden paneling.