Insurance is higher in the rural areas of SD due to fire danger.

This is typically HIGHER than option one. 

Or, what if the new interest rate is even higher and you are stuck at 6.5%? 

Also, for those whose BUSINESS (as opposed to just investment) is STR, they can scale successfully while their experience and knowledge of the industry may allow them the opportunity to uncover and recognize those few opportunities that will provide a much higher than market risk adjusted ROI. 

.: I would go HELOC for sure that would be best as others were saying the lower cost for the money changes between paying a higher rate for a personal line and typically personal lines they want a higher monthly charge as well independent from the interest rate.  

I invest primarily in a lower cost area but also own property in, and am looking in, a higher cost area.

I don't know what HELOC interest is (8 guessing), but I'm sure its much higher than a cd.

By prioritizing five-star reviews, I built a strong reputation, which led to increased bookings and higher profitability.

So if conventional primary residence rates are that high, par rates on investment properties are generally higher. 

Many “wholesalers” get all excited when getting a property under contract only to discover that a thorough inspection by a knowledgable professional results in repair costs 2 - 3 times higher than they calculated.