Using the mid-point of 8.82%, that would imply a value of approximately $515,031.

Not to imply that very good sponsors are not paying to be on the stage, but anyone with the requisite fee can be on stage at the Money Show. 

The question implies that simply trasferring debt from an amortized loan to a HELOC will result in a quicker payoff, assuming you're making the same payments on both, and at monthly intervals.

You don't need to pay a trainer or a coach, unless you have plenty of money and want to take off fast.

All I can say is .. he is a TREMENDOUS inspirational teacher & trainer.

My worry is that while I am clear on the risks (extended timeline to get a tenant in, and expensive buildout) that I am not being nearly conservative enough - do I risk this thing sitting empty for a year, or years, and finally renting well below my implied rate? 

The tone of his email implied he had been unable to reach my PM after "several attempts."

Sure you can put a mortgage on the properties and leverage them but then you have a mortgage payment to calculate in.There are some trainers out there that tell people buy 1 house a year until 10 then stop and in 30 years you will have 10 houses paid off for retirement etc.

Second problem is that by making an offer to purchase, the buyer is implying that they have the ability and the will to conclude the transaction.  

Typically they are not eligible for traditional financing which implies other funding sources (HML, private Monet, self funded, etc).