The owner took the back end profit for his park during the life of the POHs now wants to cash in again.  

It's probably unlikely anything too bad would happen excluding natural catastrophes but why take the risk if the profit potential isn't there?

I only bought sub to if there was enough equity day one to either flip with no work or there was margin to do a rehab and then sell..

That data would be sales price after remodel (the true numbers some agents really don't have the experience to be comping the property), the days on market you will experience (this is great info because you want to recycle the money quickly), and resources to sell the place fast not slowly which you do not want this because this could put your holding costs extremely high and push the property to little profit or no profit. 

Budget carefully, prioritize high-ROI renovations, and adhere to strict timelines to maximize profitability.

The 1031 exchange will indefinitely defer all tax on profit and all depreciation recapture.

Lawyers profit from the lawsuits, and politicians gain consumer support.

Ideally a HELOC is used for less then a  year project where you can refi or sell to pay back the HELOC. 5 years is a long time, things can happen and if you reduce the cashflow on both properties you'll be increasing the risk and having thinner margins.

They usually have a small upcharge on the work done but it's generally not a profit center for them. 

And then also do you typically repay each partner their upfront costs from the profits before then distributing profits?