Compared to that apartment, my duplex side has 1 more Bedroom, 40% more sqft, a nice yard, a 1 car garage.

The houses in central Il are not very expensive compared to other parts of the country, property taxes are crazy high though. 

I'd base my offer around the property's income combined with my demanded rate of return, as well as the comparable sales in the area.

If you've already closed on the property you're buying you can't do a 1031 exchange; that has to in place prior to closing. 

I believe that once I close on that first (second, currently renting out prior primary residence) property I can begin the process of refining and replicating for maximum efficiency.

Compared to Las Vegas, the crime seems benign, but I am concerned about being able to rent it out.

As it's now use-or-lose money to them, so long as you can offer a superior stay compared to a hotel then you're in business.As a furniture rental company for TDYers, we work with a lot of furnished and unfurnished apartment complexes and homeowners throughout the country to provide furniture for their occupants.

It is almost always MUCH more expensive to install (compared to just replacing an existing water heater where the plumbing already exists).  

. ** and yes: I don't know how you are arriving at 50k But go see it: based on comparable sales arrive at an ARV (after repair value): then get the estimated rehab cost from a reliable contractor: Then get the ARV $: times 65% : that will give you X: minus repair cost : and that will equal your offer priceFor example: ARV is $100k : times 65% : or 65k minus 20k in renovations: so your offer will be: $45k You can't lose with this formula. 

A couple things that jump out at me are the low taxes, reasonably priced homes compared to rents, and the landlord friendly laws.