If the goal is to "just get it done," and there are residential realtors involved that think closing in 21 days matters (in the SFR world, it does), then this honestly may be the best route.A true commercial loan will have an interest rate on-par with a 30YF primary residence SFR rate, but rather than being a 30YF, it'll be fixed for 5-7 years, and then you have to pay the mortgage off entirely, most commonly by refinancing. 30 year amortization may still be in play.

Seeing it as a great potential future home, I decided to make an offer.The offer was accepted, and I purchased the house with the intention of staying at my parents' place while renting out the home until I'm ready to buy a duplex, moving closer to my goal.

But again my goal is wealth building and wealth preservation primarily.

Crime is higher, turns are more common and the ROI in this pocket is lower. 

Also consider the cost and risks involved in obtaining a home equity line of credit.Evaluate your financial goals, risk tolerance, and investment strategy to make the best decision for your next investment. 

I do agree that the rates you are seeing are not common at all.

My guess is your electrical is grounded to your copper piping (pretty common) and you have some sort of trickle charge running through the system and grounding out through the concrete.The other option could be your gas line.

Looking forward to hearing more about your goals. 

Additionally, the structure for these porches is commonly undersized and may need repair work including but not limited to sistering joists and providing steel angle brackets at the notched beam to column connections.

All goal dependent, but if I was starting over.1.