The most important thing is to ensure your loan is covered in the event of a loss.  

I have experience in the flip, rental, space and can help with the loan, and the real estate broker piece.

We've utilized the VA loan for our current home, and this strategy has worked well so far.

More doors the better if you are using an FHA type of loan.

Possibly break loan covenants and can't cure default, lender takes back property.  

A non-recourse loan is an option if your SDIRA doesn't have enough funds.

As far as credit, you would want a score above 680 ideally to get the highest loan to value on a cash out refinance, but I would aim higher at 720+ as that comes with a significant rate drop.

There was also a loan grant available from the state of NH for first time home buyers for 3% down payment assistance.

And if it's a high amount, would you be better off just using that as a downpayment and get a standard new investment loan?

Furthermore you can vastly increase your returns through leverage using a non-recourse loan but that will definitely trigger UBIT but again the numbers can still make a lot of sense.