I've also made it a habit to ask sellers that I'm working with on an existing deal if they have other properties they are thinking about selling in the future.

The knob and tube wiring hopefully can be replaced soon, your best bet is to get quotes for the work 

I just BET you would attract the attention of a big thinking friend who would share knowledge with you.

I would bet the selling price of a Duplex would far exceed the price of a SFH especially if it's in a SFH neighborhood.I wouldn't be to anxious to convert back to a SFH.You could have a POT of GOLD

Good habit to learn early...If you agree to install vents/connectors, inform the tenants that the rental rates for these units didn't account for water usage from in-unit laundry, and that now that they are using the washer on your water supply, you're going to have to adjust the rent accordingly or start billing water seperately.Seperate metering shouldn't be too expensive, $300 a unit or so.

It is easy to talk about raising credit scores, but if habits do not change, the scores will not either

@Tom Ott - the property is in good rent-able / habitable condition with recent carpet, paint etc.

I would bet before it gets big, there is a court case where they break into those blockchains and find a murder for hire transaction or something.

The home is grandfathered in, as in, they won't demolish the home until it is either unfit for habitation or is burned down in a fire. 2.

^Obviously this is a plan I’m personally betting as the potential buy and hold person.