There are some legal considerations as well as practical considerations 1.  

I'm a GC as well and did the math, the Heloc would save considerable interest because it would average on 33% of the balance borrowed at any one time (and thats assuming constant deal flow).  

Does the bank take into consideration the income from the other units?

The boot amount is taxed as capital gains and may also trigger depreciation recapture.For example, if you sell a property for $500,000 with a $300,000 basis, resulting in $200,000 of gain, but reinvest only $400,000, the remaining $100,000 is taxable.

My team lead is a mentor of mine so to speak but in general, the people i have met through REI meet ups have considerably changed my trajectory and are real world, local examples that have helped me along the way and for free.

Does anyone take this info into consideration when looking at a rental market or is such analysis unnecessary?

Dig into reverse mortgages before pulling the trigger on anything, specifically HECM's (FHA product).

BUT I have also heard that it could trigger a due on sales clause, bringing the note fully due at any moment.

This is an example of private lending which is different than the IRA owning real estate and does not trigger UDFI/UBIT tax.

We're exploring creative ways to provide him with the cash needed for the down payment while avoiding triggering a taxable event.One strategy we're considering is purchasing his future primary residence ourselves, making the mortgage payments, and then, once we've built enough equity—comparable to the appraised value of his rental properties—transferring the title to him as a form of exchange.What are your thoughts on this approach?