If you are thinking of creating a secondary market of some sort, you'd be the third person in the last 5 years that I've talked to and answered this exact question. 

The plan is to come in and improve the NOI over the next 12-24 months then implement a strategic cash out refinance and move to long term permanent agency debt.

Investment Info:
Mixed-use building

Purchase price: $405,000

Cash invested: $20,250

Mixed use investment. 2 residential units with 1 storefront

What made you interested in investing in this type...

I have begun reading David Greene's Long-Term Real Estate Investing to ensure I do this properly.What types of data should I be looking at before choosing a market for mid-term rentals?

This could mean that he is a trend setter but he does not have the deals to back that up and has not been investing long.  

Historically, residential US mortgage rates are near their long term averages.

I’m open to both, short or long-term, in Austin or the surrounding areas (mostly considering San Marcos).

HELOC are great for short term cash needs, but not good for long term cash needs. 

Just make sure you undertand the challenges of the different Classes of properties/tenants.We operate in Detroit, which has been coming back strong for the last 5-6 years.

My business partner and I have spent the last 15 years fine tuning our property management business for single-family and small multi family investors.