A Realtor is just a designation you get for joining NAR and paying their dues. 

Double check with your lender to confirm.

It is a Depression-Era, 1930 single family home with Art Deco design elements located about a block from the city's rejuvenated downtown area, where there are shops and restaurants, and across the street from The Siloam Springs Museum.

I'm looking to redo the lawn on the property with native garden and changing some of its design like walkway, etc.

(I will call the actual zoning office to confirm)My question is what should I consider in this purchase? 

Build a relationship with them. 2) An agent could work as a designated agent (solely representing you),  dual agent(I would NOT do that), or transaction broker(they represent the transaction but give NO advice)3) No difference between the process.4) Financing is the same just walk it before offering. 

I confirmed this because a third plumber recommended by the original plumber called us trying to convince us not to pull permits after speaking with the original plumber (they all know each other).

@Dave Foster thank you for confirming that.

Meaning no designation of ADU—-but have almost all of the nice ADU features

Id also be weary and get confirmation that the tenants are actually paying and thats not the reason for them selling.