Both properties have a substantial amount of equity that’s essentially sitting idle.Would it be a good idea to tap into this equity (through a HELOC, cash-out refinance, etc.) to fund future fix-and-flip projects or purchase additional rental properties?

In beach markets, in ground pools tend to increase revenue 20% or so. 

However, about eight days later, the seller informed me that they had "changed their mind" and no longer wanted to sell.In the weeks that followed, the seller failed to provide the required documents, including HOA disclosures, the seller’s disclosure, and other essential paperwork, all of which were due within specific timelines per the contract.

It sounds like you have a lot of experience in this space, and I'm always interested in learning more.I think one takeaway is that this is a difficult asset class to own and operate, and just like @Jay Hinrichs mentioned, having a great team is essential!

And how about the loss of tax revenues during that entire time......

My investments were all what they termed private placement and was essentially funds used for lending, buying notes and recently land trust.After MIdland sprun this on us, my spouse also has accounts, I did some research but didn't see a purpose to remove our accounts at the time.I have not been with ET long enough to give comment on them and what little "issues" occured were technical.

But if you're able to figure it out and get it built, you can rent out the units and essentially BRRRR it and pull some/all of your equity out to repay your debts, yourself, and potentially keep the investment cycle going. 

Heads in beds means more revenue.

This plays into the affordability issues for tenants by allowing them to live in nicer neighborhoods for less money, yet I get monthly revenue comparable to short-term rentals.I have also shifted my focus to buying better.

Which is a tax when you do an active business in your IRA but it is essentially the same thing.