The problem is that you don't know what you don't know until you learn something sophisticated and then you realize that the stuff you learned before just wasn't good enough to achieve MASSIVE returns.I think the best kept secret is these more sophisticated calculations such as IRR.The problem is even if I let the secret out of the bag, there will probably be 90% of Investors that will say it's too difficult to understand.

I’ve run into City-Data which is a broad overview of the city as a whole, but I cannot seem to find information on a specific area of Cincinnati.

To keep it cleanest, I would think your sibling should pay market rent for the separate business space and they get their share of the profits from the building as a whole per your agreement. 

We added recess lighting, got the laundry inside the house, converted the extra room into a gym and also painted the whole house including the tiles in the bathroom (since me and my girlfriend were experts in painting from all the experience we had from the back house).

Well, yes you have late fees because you didn’t pay the whole $1000/mo for those 3 months.

Sure you could stumble across a generous 70 year old guy who will seller finance the whole deal but larger properties come with a larger price and a lot bigger down payment. 

Or the whole house?

(Likely) Step 3: If you’re a wholesaler without an ability to close, find an agent that’s comfortable working for free with a “buyer” (quotes intentional) that can’t close.Step 4: See how crazy hard it is to do Step 3 and either a.) become an agent yourself or b.) start marketing yourself.Step 5: Dodge and weave to avoid that whole “brokering with a license” thingee...

While there are several complexes, there seems to only be duplexes concentrated in certain areas of zip codes, unlike other cities I've seen where almost a whole block is all duplexes.

What I was saying about her was that it was odd, lots of other things I couldn't put in the body of the text  that sent off a huge red flag.