Leveraging existing 4plex (owned outright) for another deal

[Jefferson Smith]

(Intro note: First time poster; regular pod listener. Have begun focusing on real estate investment in just the past 18 months, doing 3 deals, so I'm a relative newbie; confident I'll have follow-up questions. And thank you!)

I own (through a trust) a Fourplex, purchased this year, owned outright (per a 1031 exchange). It was a Buy, Rehab, Rent and ____. There was no financing, so it's just a BRR_...and would like to explore the brrRefinance of some sort. (It generates ~$4400 gross monthly rent with a Zillow value (I know that doesn't count) of 540k.) 

I want to use the asset to leverage another multifamily property. What's the best route? Commercial loan 30% down with 5 years fixed (that was a local bank's initial suggestion)? Conventional mortgage on the NEXT property, and just use income from the initial fourplex, without burdening that initial fourplex with debt? Something else?