The objective is to cut down on expenses as little as possible even tho I will not have cash flow.

Remember, no system is perfect, so avoid the temptation of constantly chasing after the next shiny object.

My question is if anyone has experience with getting a 15 year mortgage and then recasting some time later (since the mortgage principle is being paid down quickly)?

Heloc rates in my area are 8.5% whereas HML was quoted at 12% and 2 points.once I finish the heloc can I pay off the principle only like I would with say an auto loan? 

You want to buy when market is tired/stagnant and sell to FOMO buyers when inventory at ATL lol kind of same principle when buying/selling stock lol

I come from the mortgage industry as a loan processor and a loan closer and those legal docs templates we used were created by a  real estate attorney, therefore, it's the same principle that allows a TC to do the same thing.

Luckily, I didn't need to tap into these funds for the initial work but I have a choice given to me: either have the contractor do more work or have that money go towards principle. 

The principles outlined can help you create your systems/processes.

These are just examples to ilustrate lenders will underwrite your property in various ways and understanding these nuances of their underwriting will help you determine the best financing option for your specific needs and objectives. 

Don’t forget ROI includes debt pay down so it has to include the principle portion of the loan payment as ROI, I don’t see that listed?