A lot of what I've read on STRs says to use AirDNA data in your analysis, so I'm wondering if this is just a lack of understanding on my part. 

If you're talking about building an interior wall to create a bedroom, this could work so long as you aren't significantly reducing living space compared to the competitive rentals. 3 bedrooms with a tiny living area could cause problems.

Why are you losing money just to keep this guy?

This along with the time of year does make it slower.  

availability of multi-family 4. ability to write my own contracts(Go off market) 5. landlord tenant laws etc......and some others.If you plan to hold long term, think of what would be most important to this type of investing i.e All the best! 

That would probably be a good market for something like this.

The US Government and the States have but one way to deal with this, taxes.

I live in Charleston, SC, and am looking to buy my first property here this year.

We put this in our offers to differentiate ourselves from other offers and we can write off this expense as a tax deduction.

Except for some commercial investors, this is virtually never the intent of a residential performing loan investor.Lately, performing notes investors are typically earning between around 10% to 15% for very little work after origination.