Here, 5% (2.5 each) is very common.

There are two components of management for you to consider: onsite and offsite management.As it relates to onsite management, the common and most generic strategy is to interview the existing tenants to find a capable, trustworthy, willing resident to be your manager.

Is this common practice?

I believe it improves the comfortability of the tenants who lives there.But it has to make Common Sense, Dollars Sense and Business Sense.  

Because I know that this is common in my area for students, are you going to furnish the apt or will your future tenants bring their own furnishings?

Unless you have a background in historic building restoration I wouldn't recommend that.That being said - definitely get an inspection and try to find an inspector familiar with old buildings. 1920s buildings have different common pitfalls to check than 1950s buildings and 1990s buildings.

(This might be common in ruralish areas but I took the time to write this down as it unfolded.)Wholesaler's purchase agreement initially had the wrong addressInsurance policy originally listed 8 units instead of four.Lawyer almost submitted articles organization as a manufacturing company and didn't know you could file for an EIN online.Few accepted digital signatures.

@John S Lewis  a few ideas, some easier than others...1) search lien records through the county2) check the system itself (panels and indoor hardware) for labels placed by the installer in case of service needs, pretty common, then call them up3) see if any neighbors have similar systems and ask them who they used, then call them up4) call local installers and ask whether they worked on that property5) looked up previous owners and ask them who installed, but check with installer about status rather than rely on the foreclosed party's representation6) Don't worry about it? 

My question is i) is it common to add a second bathroom in the basement, and ii) the basement is currently unfinished - would I need to finish the basement in order to have the second bathroom?

Landlord is responsible for roof, structure and common area maintenance (costs of which get reimbursed by Tenants)Of course, leases can have variations of the above.