house is electric. 

There's the insurance adjuster and then quotes for drywall demo, flooring demo, possible mold remediation, drywall replacement and mud, possible electrical involvement, priming and painting, carpet and pad.  

Some other reasons properties may not sell so fast.... sink holes, foundation issues, need for all new plumbing, need for all new electrical, ghosts, history of a murder on property, bio-hazards, methamphetamine cooking, occupied by squatters or professional tenants, neighborhood violence, noise (airport, railroad, highway), smell (animal farms, slaughter houses, industrial plants), natural disaster danger (flood, landslide, tornado, hurricane, earthquake, volcano), finicky seller.Have you been to the neighborhood at all times of the day?

I would factor in 10k a unit, so basically double your repair costs, and that is if the duplex does not have anything major wrong with it like foundation, or electrical rewire, or replacing main water lines. 

Even electrical and plumbing(safely).

I used Kast Electrical Services (from Homeadvisor).  

In addition, the water department, electric company, sewer department, other landlords all know everybody.  

Expect to spend 10-15K on a smartly purchased used one -  assuming your pad, electric, and plumbing are all effectively setup on the land.

We help people through church or other organizations who can't pay their electric bill.  

You can sell solar electricity.