We would like to have a similar type of product; a low down payment loan with a construction component. 

Doing so right before a 1031 has always opened the door to a claim that you took title primarily for resale and not to hold for productive use. 

Be sure to ask though I might have the wrong product or there might be a better one.

If you are working with a conventional lender, refinancing/ HELOC follows the same general process as a new loan (underwriting)...there are some exceptions to this, but it depends on the lender/loan product, and situation...

My thought process: Cap rate is pretty low at 3.2% and I feel like appreciation will slow considerably and potentially correct as interest rates eventually rise, lumber costs decline for new builds, and homeowners start selling as covid fears subside.

When comparing apples to apples across the board with different lenders you will need to know what the interest rates are, what % down you will be using, what the total lender fees are, any points being charged & what loan product specifically you are looking at. 

PS even if you had a lawyer draw it up if your funding source declined or could not fund the whole thing you would still be stuck with not a lot of recourse other than threatening letters and useless litigation.

You will need to let your mortgage company know as the terms of the loan product could be dependent upon  owner occupied use or that of SFR rental alone, and you don't want to have anything come up there.

Relying on parking companies to manage and improve your "product" is paramount.

@Steven Wilson Thank you for sharing the the HML contact with me, ill be sure to check them out.They are really good with long term products, but dont expect it to be any easier then a traditional lender.