I am attempting to supplement the rooms revenue with alternate and/or non-traditional forms of ancillary revenue. 

Check out this website: http://www.myfico.com/credit-education/credit-chec...TLDR: Multiple inquiries from auto, mortgage, or student loan lenders within a short period of time are treated as a single inquiry.My best recommendation is to call many lenders and talk with them on the phone, figure out if they answer the phone, what their process is, if you have a good vibe, and how they handle tough questions regarding duplex/using one side as a rental to supplement income.Narrow down to 2-4 lenders that work well and get a prelim quote from all of them in "a short period of time" and choose your favorite.

I have talked to him over past few months about buying a rental property for supplemental income and getting into the real estate realm.

Then get a side hustle to supplement your income.

Raise the rent to market, not close to market, there is never any justifiable reason to supplement a tenants rent.

He has had a free ride for too many years with his previous landlord supplementing his rent.

Why would you choose to supplement your tenants rent out of your own pocket.

REI) to supplement your 401k. 

I consider myself a successful investor because I am able to live off my rentals with no supplemental income if I choose, which is the goal of many in this forum.

Long story short, I began researching the deregulation of energy, and found that I could become a broker for lack of a better term for energy and supplemental services.