Pretty much any regular bank / lender is going to require themselves to be in first position on all the properties... so I don't think a HELOC type solution is going to work across multiple properties with multiple lenders.  

I have many questions that need answers so I will likely be a regular here in this chat.

Transitioning from builder’s risk to a regular property insurance policy might be the way to go if the sale takes longer than expected.

Maybe you could extend the closings with some additional earnest money (even if you release it) and buy the time so you can simply do a regular 1031 exchange.  

Still no solution yet from them though after I check in every few days.

You should treat it as a luxury package rather than regular STR. 

Section 8 guarantees part of the rent, which is great for income stability, but the building will have regular inspections to meet Housing Quality Standards (HQS).

We’d actually love to invest in Bergen County NJ, but the numbers just don’t seem to check out at the moment.Also, thanks for the reminder not to rush into something just to do a deal. 

If you were to say to them, for example, "I see you have a baby coming, so I'm not going to renew your lease since you are regularly late paying now

I see it somewhat regular of people who got into a "deal" with HML, to do a Brrr and now it's half done reno and there desperately trying to sell it as-is to bail them out.