I'd bet if you really add up the expenses it's not as good of an investment as it appears. 

You'll find his cookie-cutter-template seven-page Web 1.0 beta website for his obviously smallish company, GH Plumbing.

From reading her posts, I'd bet @Helen Kirk has some insight on this....

Ziaur,There are lots of lenders who can get you 1-4 units with 30% down, we can help you with the financing, also out of state you can get more bang for your bucks, your best bet would be buy 5 properties for about $40k each and get rent of about $850 each, that should put you at the ROI you are looking at. 

Your best bet is used transactional funding.

I had never heard of that before and thought it was an interesting "outside the box" concept.I also did sort of a fundraiser/contest once where I offered my web development skills (a free website) as a prize for entry.  

But even then I bet I could negotiate upfront my required schedule or they get terminated.

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