I am wanting to sell some very secure cashflow from NNN leased commercial property with BBB- or better national credit tenants.

In the first instance, you simple need a partnership agreement (or a company) with you as the operating/general partner to make it official.In the latter case, you may find yourself in the realm of securities regulation which will add much more cost and effort to your fund raising.

Technically that is not correct, and could bite us in the butt, but I haven't had to fight it yet....After they vacate the property, within 45 days, you need to send them a final accounting of the damages, cleaning, etc and how their security deposit was applied..

Our securities attorney is working through this right now.The good news is that we'll be offering a SaaS service for principals to use our technology soon.  

The more sophisticated attorney's know how to do this, one of the advantages is that no funds are exchanged in advanced and the original seller does not have to be made aware of the subsequent transaction.

In the past, it wasn't worth dealing with an aggressive tenant, so I just waited it out (after experiencing enough loss of sleep).What you might consider is offering the tenant a portion of their security deposit back on the day they hand over the keys (if there's no damage) instead of making them wait, in exchange for cooperation in showing the unit.

I kept getting denied so I got a secured credit card.

Which in theory you can do whatever you want with - but the investor won't have their asset secured by real estate.  

Is there a product available to LLCs that’s very similar to a HELOC, that is secured against the asset, but doesn’t have extreme costs like hard money, typical portfolio loans for flippers, etc.?

Congratulations on securing your first flip.