There are a few more “big ticket” items that need to be considered (Minisplits & landscaping) but most of the major costs have already been accounted for on this property.We currently have a 30 year conventional mortgage with a 7.125% rate on a purchase price of $750k. 

If $100-$120 aligns with similar properties, then it’s a fair rate—especially considering the size of the home and the work involved.

(I also don't understand how you have a hard money loan with a rate of 7.25%...)offering an equity position that you then buy out in just a few years seems like way too much complexity and risk when you say you just need 30K. 

It’s quite appealing as a long term investment - even at today’s rates.

During this initial research I read several articles which state that coverage in high risk states has significantly declined since 2015 due to policy rate / deductible increases such as what I am outlining above.

There seems to be an endless number of these listed with attractive cap rates.

Only difference is the $10K is in your bank and the interest starts so you are paying on the full $10K over how ever many years they offer.Lastly, depending on your first mortgage rate it may be best to just do a "Cash out refinance" becuase its over a 30 year mortgage and the rates are lower then both Heloc or Heloans. 

(To clarify, the metric I'm talking about isn't true cash-on-cash or cap rate, under strict definitions.

Routine maintenance and unforseen maintenance costs; insurance rates (they are increasing all over), property taxes and vacancy rate.

Nightly rates, occupancy and amenities.