Remember too, the interest rates are a commodity item and are dependent on current economic climates.

The roughly $110 million plant, which is expected to employ about 580 workers at build-out, represents a major economic score for the Hill Country city, considering the public incentive package offered to land the project included a $3.3 million land acquisition grant and $1.8 million in infrastructure improvements.https://www.bizjournals.com/au...

I'm trying to educate myself on the process (if I decide that the economics make sense) of scraping my house and building a 12-unit apartment building. 

First step is to look up the property on the Zoning map to see what you can build by right and that you have the appropriate property line setbacks.If so, then it can be a good next step to familiarize yourself with the building inspectors and the process.If not, then it's best to go to an experienced Zoning attorney and discuss whether it's possible and economically feasible to try to build a 3 family on the site.

The remaining economic life for the home is only 15 years and the term requested was 30.

Unfortunately in the current economic climate some landlords will have to sell their properties.

Depending on the penalty, if at all, will impact the economics of your refinance. 

One of my daughters economic mentors a few years ago,  explained how they converted their old garage, detached, to a unit for STRs. 

Economic Update(Monday, June 28, 2021)Should Investors Wait Out this Crazy Housing Market?

Work on your credit while this is happening and you'll come out on the other side of this bloated economic insanity with REPS and CRED -- two superpowers to have when the dust settles on this.