I’m at the stage where I feel like if I get one I’ll continue to get more and build my portfolio I’m just not sure how to get that first house To flip.

I’ve encountered people like this at every stage in life.

We're currently in the financing and deal finding stage of things. 

We purchased our current flip with our heloc and maxed it out, however we are in the last stages in finalizing a refinance mortgage, we are waiting on a lien (that should have been removed at closing, the company hasn’t released it, it’s a total headache) to be removed.

Go with them through every stage, from having notice prepared and posted, to filing for the court hearing, to being in the courtroom when they appear in front of the judge/magistrate (whatever they call the authority in your state).Ask the attorney or their assistant about any documents/procedures you don't understand. 

He's putting a lot of trust in me, so I want to be sure his capital is fully his at all stages. 

Airbnb estimates ~1600/mo average, and I think it is a bit conservative given the location next to public transportation, "coolness" of the unit (100+ year old building that will stage and photograph well), and relatively underwhelming alternative Airbnb and hotel options.Furnishing everything is my biggest unknown that I'm working on, but I would greatly appreciate hearing about any red flags/concerns/oversights that jumped out at you while reading this.

I think depending on how far you are away from your properties and if you are in the beginning stages and it's manageable from a time standpoint it makes sense to do it yourself. 

At this stage you need to be looking at value add long term.

Far too many get stuck in the "paralysis by analysis" stage, thinking they just don't know enough to get started.