In fact, the contents of the estoppel agreement are deemed conclusive even if they are erroneous.

If I decide to sell it in 10 years and the heirs contest it, is there some kind of occupancy/possession law on my side for having occupied the land (even if erroneously?)

Granted, we err on the side of doing things right the first time, but projects like new roof or new windows cost a lot and don't have that much impact on the appraisal, as long as the existing components are still in acceptable condition.

I would counter your erroneous statement with this: "What causes 99% of projects to fail is the homeowner/investor/flipper having zero clue on how to find a property with decent upside, choose a good Contractor, manage a budget, stick to the plan, stay out of the way, etc

See how all this plays out before you commit yourself to erroneous processes because you advised some "mentee" to follow your lead when you hadn't yet invested the effort to learn the dance.

Currently, I have very low hopes and figured I reach out to this community to see if anyone can help with a direction, options or other that will not be erroneously expensive.

As part of that they need insurance.All other work requires a Home Improvement Contractor (HIC) REGISTRATION --- its always erroneously called a licence. 

Some erroneous information posted here.An REO means that a lender has foreclosed on their mortgage, whatever lien position.

Verbal agreements should be taken with caution.Remember, if something feels off, it's better to err on the side of caution.

This is all due diligence you should be doing before wasting other people's time and erroneously putting properties under contract.