I do not anticipate a complete gut job and rewire, but there is some potential existing above only one unit.

Sell the existing home and pay off the first $300k loan. 

Quote from @Scott Vaeth: A bird in the hand is worth two in the bush.I see so many new investors lose thousands (or tens of thousands) every year by making rookie mistakes with existing rentals.

Refinance Existing Loans- Lower Interest Rates: Since nine out of ten properties have commercial loans, consider refinancing to secure lower interest rates.

The majority of existing houses were built in the 1930s, contributing to the unique character of the neighborhood.

So, any small errors if they exist are likely caught then because we are all looking at the document and discussing each section. 

But again, even I went with a new build as there are always pros and cons.That being said, some of my clients go with the existing build route, as they know the previous owners typically have already made the necessary repairs/updates that the builder skipped out on. 

Quote from @Jacob Palmer: Existing contracts transfer with the sale.

That cash flow on paper is non-existent in reality and I don't think the path of gentrification is predictable - will it appreciate enough to make up for all my repairs, etc? 

I've made many great connections, educated myself on topics I didn't know existed before and have taken actionable steps in my personal investing business that I wouldn't have done otherwise.