o Commercial loan, sort of - they are 30-year fixed DSCR loans with private national lenders.o We close in an entity/LLC 99% of the time - very rarely do we receive a request to close in someone's personal name.

You would need an appraisal, or some sort of FMV as of the date of transfer, which would essentially be your proceeds.Please don’t make the same mistake twice!!

Ideally would meet in person but open to some sort of hybrid structure as well.

You'll need to provide Entity Docs for each LLC that is a part of the transaction so that the underwriters can review them all the way down to the natural individuals/warm bodies. 

Doesn't have to be 7 days a week or even 8 hrs a day but some sort of set schedule so new people can sign up for units.

He was decidedly more excited about that idea.In terms of money, my initial thoughts were that the equity in the property would change over time as individuals contributed more throughout months/years until an agreed amount of parity was reached based on whatever the property called for: i.e. everyone owning a 2bed/2bath had contributed the same amount of capital, that sort of thing.

Mostly my question is: can I pull a HELOC on an investment property or is there some sort of rules that only let you pull a HELOC on your primary residence?

You need to contact the governing body that has jurisdiction over the zoning laws for either the incorporated or unincorporated of the county or city for the plot you are interested in building on.  

Do they offer some sort of Guarantee? 

The interest on your primary is sort of deductible.